Related
I've seen a lot of people complaining about not being able to boot after using A2SD for a while and I think it's definitely necessary to make clear the danger in using A2SD and some ways to prevents them.
Do not move /data/data to SD.
You can safely move /data/app and /data/app-private to SD. Be cautions with /data/dalvik-cache. (See below)
Make sure the ext2 partition are mounted with noatime and nodiratime (rom maker's job)
Do regular file system checks (using Linux)
Back up your ext2 partition and redo them regularly
Here're the theories:
(NAND) Flash memory has two serious limitations when used to store frequently changing data: you cannot do random write unless you erase a whole page first and any bit can only be written a limited number of times (typically a couple millions). When one bit in a page is detected to be faulty, you lose the whole page. (More details: http://en.wikipedia.org/wiki/Flash_memory#Limitations )
Most mobile os vendors overcome this problem by using special file systems, namely yaffs and jffs, which arrange files according to page size and do write operations only when necessary. They also provide journals so hardware faults could be reliably detected and corrected.
EXT2, which is the file system used in A2SD, DO NOT have these features. It may stupidly allow several pages to be erased hundreds of times of just to write some small files into it. Things are made even worse because some fixed part of the file system (inode table and bitmap) has to be written EVERYTIME a file operation is done. The will accelerate the wearing of those pages and when they become inaccessible, you lose the whole file system.
A2SD would work fine if you only move /data/app to it, because the application files are never modified. It is a completely different story for /data/data because the sqlite databases in there are modified almost every other second!! (And I suspect the OS commit them to disk very often to ensure data integrity.)
In addition, android does not have system check tools for ext2, so it will not be able to detect any problem with the file system until it’s too late.
Edit:
I am not sure how frequent the system updates files in dalvik-cache, but I would say you only move it when you are running out of space in /data.
(Also changed title)
billc.cn said:
I've seen a lot of people complaining about not being able to boot after using A2SD for a while and I think it's definitely necessary to make clear the danger in using A2SD and some ways to prevents them.
Do not move /data/data to SD.
Do regular file system checks (using Linux)
Back up your ext2 parition and redo them regularly
Here're the theories:
(NAND) Flash memory has two serious limitations when used to store frequently changing data: you cannot do random write unless you erase a whole page first and any bit can only be written a limited number of times (typically a couple millions). When one bit in a page is detected to be faulty, you lose the whole page. (More details: http://en.wikipedia.org/wiki/Flash_memory#Limitations )
Most mobile os vendors overcome this problem by using special file systems, namely yaffs and jffs, which arrange files according to page size and do write operations only when necessary. They also provide journals so hardware faults could be reliably detected and corrected.
EXT2, which is the file system used in A2SD, DO NOT have these features. It may stupidly allow several pages to be erased hundreds of times of just to write some small files into it. Things are made even worse because some fixed part of the file system (inode table and bitmap) has to be written EVERYTIME a file operation is done. The will accelerate the wearing of those pages and when they become inaccessible, you lose the whole file system.
A2SD would work fine if you only move /data/app to it, because the application files are never modified. It is a completely different story for /data/data because the sqlite databases in there are modified almost every other second!! (And I suspect the OS commit them to disk very often to ensure data integrity.)
In addition, android does not have system check tools for ext2, so it will not be able to detect any problem with the file system until it’s too late.
Click to expand...
Click to collapse
these are very good points. Actually come to think of it we better mount the ext2 partition with noatime. Because right now every read will wear the flash down. flash storage is really not meant for ext2 filesystem.
knaries2000 said:
these are very good points. Actually come to think of it we better mount the ext2 partition with noatime. Because right now every read will wear the flash down. flash storage is really not meant for ext2 filesystem.
Click to expand...
Click to collapse
In JF1.5 build it is mounted with noatime, i believe:
#mount
/dev/mmcblk0p2 on /system/sd type ext2 (rw,noatime,nodiratime,errors=continue)
But I totally agree with the point of the thread /data/data should not be moved to sd. Not that it's only dangerous (as described), I even don't see any advantages of it.
Dimath said:
In JF1.5 build it is mounted with noatime, i believe:
#mount
/dev/mmcblk0p2 on /system/sd type ext2 (rw,noatime,nodiratime,errors=continue)
But I totally agree with the point of the thread /data/data should not be moved to sd. Not that it's only dangerous (as described), I even don't see any advantages of it.
Click to expand...
Click to collapse
really. that's good, but I am running haykuro's build right now and it is not mounted with noatime. I will have to change the init script.
I'm using JF's 1.5 A2SD build, and I'm pretty certain I moved over /data/data. I didn't really ask myself the question when doing it, but what exactly is stored in /data/data? Is there a command I can run to move it back off the SD card?
Are ext2 and fat the only supported file systems in the android kernel? If not maybe it would be best to move to a wiser file system.
Rekna said:
Are ext2 and fat the only supported file systems in the android kernel? If not maybe it would be best to move to a wiser file system.
Click to expand...
Click to collapse
Yeah, why can't we use yaffs etc?
Dimath said:
Yeah, why can't we use yaffs etc?
Click to expand...
Click to collapse
i don't think most partitioners support yaffs
i know the partition manager on ubuntu 8.10 doesn't
tubaking182 said:
i don't think most partitioners support yaffs
i know the partition manager on ubuntu 8.10 doesn't
Click to expand...
Click to collapse
Indeed, and I'm fairly sure that's why it hasn't been done. But keep in mind several million write cycles is a heck of a lot and apps only really write their data caches occasionally, so it'll likely be a while before anything bad happens(on the scale of years) so this is slight sensationalism. Actually the term "cache" is a slight misnomer here since it's really just storage the apps use for temporary data. If it were used as some kind of extended RAM or a real cache then I could see problems but with what it's used for it should be a non-issue.
billc.cn said:
Here're the theories:
Click to expand...
Click to collapse
SD cards are a form of removable flash that have their own write controllers. In most cases, the write controllers also perform wear levelling. This means even if a program writes to the same file on the sd repeatedly, each time it writes, it is not writing the same physical location on the flash. The reason for this is because due to the way flash works, entire blocks have to be erased before they can be rewritten. To make writing faster, the memory controller keeps a list of empty blocks that are ready to use. When a file is changed, the entire file with the new changes is written to a new memory block and then the old block with obsolete data is then reset to zeros (data deleted).
That said, I still think A2SD is a red herring that only contributes to newbies spamming these forums.
jashsu said:
SD cards are a form of removable flash that have their own write controllers. In most cases, the write controllers also perform wear levelling. This means even if a program writes to the same file on the sd repeatedly, each time it writes, it is not writing the same physical location on the flash. The reason for this is because due to the way flash works, entire blocks have to be erased before they can be rewritten. To make writing faster, the memory controller keeps a list of empty blocks that are ready to use. When a file is changed, the entire file with the new changes is written to a new memory block and then the old block with obsolete data is then reset to zeros (data deleted).
That said, I still think A2SD is a red herring that only contributes to newbies spamming these forums.
Click to expand...
Click to collapse
Which is exactly why I made my new method that's able to deal with a lot of user mistakes and can be incorporated into ROMs to make it take almost 0 user effort
Dimath said:
Yeah, why can't we use yaffs etc?
Click to expand...
Click to collapse
yaffs on SD cards can in some common cases invalidate the wear leveling in hardware that SD cards do, as they so the wear leveling in software.
You are simply understimating ROM makers, SD cards are different from the internal flash in that they do auto wear leveling, that's why you can put common filesystems like FAT which have statically placed allocation tables and writes to the same logical sector will always land on very different places in the card every time.
Yes, noatime will help a lot as it will _reduce_ writes to your SD card.
ext2 is not journalled so it will have less writes too than ext3 or any other journalled filesystem.
So ROM makers are already doing a good job, don't understimate them please.
Im trying out a theory. I running JAC Hero 2.3 and wanna try running the swapfile on the /data partition. I moved app_s over to /system/sd and used swapper app to create the swapfile but android doesnt seem to use it. when i run free It says Total/used/free are all 0 but the swap file is 34 meg. I tried putting it in a sub folder and chown root.root on the folder before setting up and still no luck. Anyone have any ideas why it wont work on /data or how to get it to work on /data?
Once you run swapper go into the setting and change the location of your swap file from /sdcard/swapfile.swp to /system/sd/swap.swp ( see sxfx post[url]
you don't want to do that. Swapping involves a lot of writing and erasing, it'll wear out your internal chip and you'll start experiencing reduced capacity, write cycles for nand are even less than for flash memory!
jubeh said:
you don't want to do that. Swapping involves a lot of writing and erasing, it'll wear out your internal chip and you'll start experiencing reduced capacity, write cycles for nand are even less than for flash memory!
Click to expand...
Click to collapse
not to mention, swapon as implemented (on every build i've tried) doesn't work on a swapfile stored on a yaffs2 partition
jubeh said:
you don't want to do that. Swapping involves a lot of writing and erasing, it'll wear out your internal chip and you'll start experiencing reduced capacity, write cycles for nand are even less than for flash memory!
Click to expand...
Click to collapse
Actually /sdcard/ is your fat32 portion of your sd card, /system/sd/ is the ext2/3 of your sd card.
Also I have done a bunch of research on this write/read fiasco just because of android.
And even if you set a swap file to your SD sure it will shorten your life of the card but it will still last you at least 2 years.
I have been using USB devices on linux as swap locations forever now and I still have thumb drives that have been used and abused for months and months as a swap place and they are still pulling strong.
As for the internal chip, Im not sure what you mean by that?
Even if you could put swap on the internal flash, its not going to be faster.
Putting swap on the internal flash will make things slower as the internal flash is about 3 to 5 times slower than a class 6 sdcard.
you're comparing using a flash drive for swap in a full blown computer that probably has around 1-4gb of ram, the swap file is hardly ever touched, unless you're running a lot of applications at a time. Dream has only 90 mb available to dalvik, and rosie is a big fat... lady... plus linux/dalvik manage memory in a different way, so files are often dropped to swap and they dont stay there for long (maybe in a 256 swap, but not in a 32 mb one).
the OP also is talking about moving his swap to his internal storage (chip, nand, whatever), as he thinks it's having no effect working from the sd card. Personally, i think that both a2sd and swapper are flawed. They're overcompensating for an os that was not meant to run on that device, and the real work should be in porting (as in developing, not just file-swapping as most "devs" do here) a launcher app that we can feel comfortable with running on a stock android system with stock (or slightly improved) libraries and that we can call comparable to rosie. Just look at ahome or dxtop or openhome, they're good, solid, great looking home replacements that work as well or better than rosie, but they run out of the stock libraries. I wonder why nobody has made a free, open source home replacement app yet
jubeh said:
you're comparing using a flash drive for swap in a full blown computer that probably has around 1-4gb of ram, the swap file is hardly ever touched, unless you're running a lot of applications at a time. Dream has only 90 mb available to dalvik, and rosie is a big fat... lady... plus linux/dalvik manage memory in a different way, so files are often dropped to swap and they dont stay there for long (maybe in a 256 swap, but not in a 32 mb one).
the OP also is talking about moving his swap to his internal storage (chip, nand, whatever), as he thinks it's having no effect working from the sd card. Personally, i think that both a2sd and swapper are flawed. They're overcompensating for an os that was not meant to run on that device, and the real work should be in porting (as in developing, not just file-swapping as most "devs" do here) a launcher app that we can feel comfortable with running on a stock android system with stock (or slightly improved) libraries and that we can call comparable to rosie. Just look at ahome or dxtop or openhome, they're good, solid, great looking home replacements that work as well or better than rosie, but they run out of the stock libraries. I wonder why nobody has made a free, open source home replacement app yet
Click to expand...
Click to collapse
You make a very good point about computer having 1-4gigs of ram and not needing a swap file.
Honestly I almost never run a swap file on a computer that has more then 1gig of ram.
Plus90% of the time when I do run a swap file is when Im running a live distro of linux of a cd, but also 90% of the time I run the distro from the flash drive instead of cd cause its much faster.
So now imagine how many reads/writes I abuse that flash drive with by running a full OS on it.
Also I don't understand how a2sd or swapper is flawed? Just because they do their job? I mean it's not really our fault that they made the G1 with a little less memory spaces then we would like it to have.
But that's exactly why we have tools like swapper and a2sd. Plus no one is really forced to run these roms on the G1 phone and those of us that do realize that we have to take extra steps in creating tools to help it.
And that's not only true for the G1 but anywhere in the computer world these days.
dwang said:
Even if you could put swap on the internal flash, its not going to be faster.
Putting swap on the internal flash will make things slower as the internal flash is about 3 to 5 times slower than a class 6 sdcard.
Click to expand...
Click to collapse
I'd like to spread swap over the sd and internal storage if possible -- should make paging a lot less evident if priorities are set up properly.
dwang said:
Even if you could put swap on the internal flash, its not going to be faster.
Putting swap on the internal flash will make things slower as the internal flash is about 3 to 5 times slower than a class 6 sdcard.
Click to expand...
Click to collapse
internal memory is faster. class 6 guarantees 6mbs read/write times but doesnt mean the bus can support those times. if you run a test copying something to /system/sd and to /data you will see /data is faster. as for those saying it will degrade the internal memory, that is not the case being the flash memory inside is designed to have much much much more read/write cycles. Think about it in a stock G1, this is where dalvik-cache is writen to as well as email, sms, user settings, cache for browser and uTube. Do not confuse internal flash memory to sd card flash memory
Are you sure about that? This guy has some test results and it indicates that a class 6 sdcard is much faster than the internal flash.
http://forum.xda-developers.com/showpost.php?p=4059520&postcount=15
MonkySlap said:
internal memory is faster. class 6 guarantees 6mbs read/write times but doesnt mean the bus can support those times. if you run a test copying something to /system/sd and to /data you will see /data is faster. as for those saying it will degrade the internal memory, that is not the case being the flash memory inside is designed to have much much much more read/write cycles. Think about it in a stock G1, this is where dalvik-cache is writen to as well as email, sms, user settings, cache for browser and uTube. Do not confuse internal flash memory to sd card flash memory
Click to expand...
Click to collapse
dwang said:
Are you sure about that? This guy has some test results and it indicates that a class 6 sdcard is much faster than the internal flash.
http://forum.xda-developers.com/showpost.php?p=4059520&postcount=15
Click to expand...
Click to collapse
That's interesting. Going to have to try that test out. I just noticed when xfering stuff to /data it was faster then to /system/sd. If it is then touche my friend.....touche
Is there a cogent reason why the SD card cannot be partitioned without a FAT32 filesystem? From all the benchmarks I've ever seen, EXT4 kills FAT32. However, when I tried using an SD card partitioned with only an EXT4 partition, vold (the volume management daemon) wasn't happy at all.
I can manually mount the volume from the shell, but that does no good as far as android recognizing that the partition has been mounted.
I'd be willing to hack up the vold source code if it would be useful, but I just want to know if anyone has any thoughts or experience on the issue.
This question has been asked in the past, but no one has every replied to it. Is there no one with experience in this area?
Thanks
bump........
That's just what is most common and what it looks for. You could try and look at the apps2ext scripts for mounting etc.
What real performance gain could you see by using just ext4 in this scenario, my guess it nothing.
There's possibly no speed difference, though benchmarks with flash do show ext4 to be faster. The bigger point though is why have both an ext and fat partition, when you can have only one?
Also, I don't see why this should be an issue. 'mount' can auto-discover the filesystem type of a partition, so the only reason this shouldn't already "just work" is because vold is forcing it to be FAT. I find this ironic given that the main system partitions are actually YAFFS2.
Information
JIT Compiler
Going Deeper With Android 2.2′s JIT Compiler
by Quentyn Kennemer on May 26th, 2010 at 3:09 am
Before the official Froyo announcement at I/O, we’d learned that an Adobe employee’s phone was running at ridiculously high speeds. Most outlets quickly chalked this up to the possibility that Google implemented a Just-In-Time compiler for their Dalvik Virtual Machine.
Sure enough, they confirmed our suspicions at the keynote in San Francisco, and we even got a taste of real-world performance (there’s no “theoretical” performance hikes here, folks). We know what JIT does, but I’m sure there are a lot of non-developers out there that can’t understand how it’s able to provide the huge bump in performance for Dalvik.
Technical lead for Android’s Dalvik team – Dan Bornstein – signed in with a blog post over at the Android developers site going into a bit more details about what’s really going on beneath the hood to significantly improve performance of Android (in certain cases) without needing to touch the hardware. Thankfully, he puts it in plain English so you can get – at the least – a pretty basic understanding of what’s going on. Head over there now if you want to learn more about what makes your Froyo so sweet.
Linux-Swap
What is SWAP?
Swap space is an auxiliary storage, such as a portion of a hard-disk, which can be used as memory by the operating system when system RAM is insufficient. This is especially useful on systems with very little system RAM, such as most DD-WRT compatible routers, as it helps prevent the system from running out of memory when multiple background processes are installed.
The difference between Froyo A2SD, A2SD and A2SD+
One of the glories of using Android is having an SD card for storage rather than having internal-only memory. Thanks to Android’s Linux blood, you can even harness the power of the SD card beyond its usual file storage capabilities. On Android, your internal memory is precious and you do not want to install games and applications – especially those which are up to 50MB in sizes – on your internal memory just to make your phone run slower. Instead, you can install the applications on SD card and let your phone take care of the system apps instead, saving more internal memory and speeding up your phone.
The Partitions
Android natively supports fat32 partition. However, thanks to the Android community, support for swap and ext partitions can be enabled too. Depending on the ROM, some can support up to ext4, while others support up to ext3. The explanation about the differences between these partitions is indeed very lengthy and not part of our chapter today. What is important to know, is that Android has support for fat32, swap, ext2, ext3, and ext4 partition support.
Your SD card is by default formatted to fat32. In order to use swap and ext partitions, you need to repartition your SD card. There are several ways to do this, but the most common way is by using a custom recovery installed on your phone (ClockworkMod or AmonRA recovery). Swap is virtual memory which uses extra space on your SD card for virtual memory. However, since Android already has DalvikVM, swap is not really needed. I myself don’t use swap space on my SD partitions. Ext partition is extended partition which was the first ever type of partition created specifically for Linux. It is based of the standard UNIX file system and was designed to overcome the limitations of Minix file systems. Ext 2 is second extended partition, ext3 is third extended partition and ext4 is the fourth extended partition respectively.
Dalvik Virtual Machine
One of the best functions of Android has to be the Dalvik cache. Dalvik cache is a wonder from the point your Android starts up, runs, hibernates and all the way till you device shuts down. Dalvik cache collects the information about the installed applications and frameworks, and organizes them into a writeable cache. Under this writeable cache, it stores the “optimized” bytecode of the applications which is used by the applications themselves later for a smoother operation. This dalvik cache can grow immensely huge as more applications are installed on your phone. It is safe to wipe dalvik-cache. It will be rebuilt again when the phone boots. This also explains why your phone takes ages to start up for the first time. As for my Nexus One, having about 145 applications installed, it takes about 13 minutes to build the cache.
If you ever extract an APK installer file, you will always find a file named classes.dex. This is the file Dalvik finds to build the cache. What makes the process slow? APK is an archive (which is why you can open it up with an unarchiver such as WinRAR or 7-Zip). Being an archive, it provides limited write access to the files contained within and the fact that archives are compressed. Not to forget, APKs are encrypted archives too. Therefore, DalvikVM has to extract the classes.dex files and build the Dalvik table accordingly which makes it easier to write data on it too. With this collective set of data, the Android OS no longer needs to index the applications and find their classes.dex when the phone is already running. Instead, it will just look into one place, and will know what to do next. Nifty huh?
To know what is going on inside the Dalvik VM, you can read about it here.
Froyo A2SD (F-A2SD)
When Froyo was released to Android community, one of its new features was the A2SD implementation. F-A2SD uses fat32 partition natively for application storage. This means, all you have to do is just slot in your SD card and its all ready to go. There is no need to partition the SD card whatsoever. This was a great effort from Google to include A2SD to the Android OS as it gives you an option to choose which applications you want to move to SD card, and which you want to leave on internal memory – BUT – with a condition! If the application developer decides to protect his application and not include A2SD support, you would not be able to move it to SD card. One major problem that F-A2SD has is that it only uses fat32 partition. This way, when the SD card is mounted to the computer, the applications become inaccessible. Not only that, if the applications have widget support, the widgets are removed too when the SD card is mounted. This can become rather a hassle especially if you have to mount your computer several times in a day.
A2SD
The A2SD method is much more interesting. It harnesses the glory of ext partitions. This way, the applications (protected or non-protected), will all be installed on the SD card ext partition. The good thing about ext partition is that when you mount your SD card, the ext partition is NOT mounted together. This said, when your SD card is mounted, the applications will still be accessible and separated from the files and folders on your fat32 partition. On A2SD, the dalvik cache resides on the phone memory.
A2SD+
A2SD+ takes the A2SD one step further. Its pretty useless to have a 512MB A2SD capacity if your dalvik cache is still on phone memory and you have lots of applications installed. This is because the dalvik cache can become pretty huge and just by using HALF of your A2SD’s ext partition, your internal memory can become FULL because of dalvik. Therefore, in A2SD+, the dalvik cache is also moved to SD card. This way, your internal memory is free as a highway. However, remember that Dalvik cache is accessed very frequently. If you have a slow SD card, the overall performance might be affected. I recommend using a class 6 or class 10 SD card for the purpose.
So make your pick guys. In Android’s world, you always have choices. Depending on your needs, use the partition that satisfies you. Hope this article clears any misunderstanding that anyone might be having. Cheers~
Filesystems (post is for galaxy s but all android is ~ same in filesystems)
Reality behind RFS Lag
Background
All data is stored on an 8gb or 16gb MoviNAND chip, of which 2GB is ‘system data’, and the rest is for user storage. The MoviNAND is one of the first mobile ‘smart SSD’ chips. That means that the MoviNAND handles all operations such as data wear leveling, physical data lookup, as well as having it’s own internal buffers. This cleverness is both good… and very bad.
RFS
RFS has a fairly badly written driver, that will call an fsync on file close.
Basically, RFS runs in ‘ultra secure’ mode by default. This security may not be really needed – I personally don’t want it if it means enormous slow downs. It also doesn’t help data security if the system/app is holding a file open, only if it closes the file. The MoviNAND is also fairly smart, and appears to write it’s cache to disk before turning off, and also appears to have capacitors to keep it alive for a little bit of time in the event of a power cut.
SQLite
Most Android apps use SQLite – a fairly simple database that is easy to embed. Sqlite has ‘transactions’ – not real transactions, but a transaction in sqlite is where the database is locked for the duration of a database write, and multiple databases writes can be included in one transaction. At the end of a transaction, sqlite will call FSYNC on the database file, causing a possibly long wait while the MoviNAND does it’s thing. Certain applications will not bunch up writes into a single transaction, and will do all of their writes in new transactions. This means that fsync will be called again and again. This isn’t really a problem on most devices, as fsync is a very fast operation. This is a problem on the SGS, because MoviNAND fsync is very slow.
The various fixes and why they work
Native EXT4 to replace RFS (Voodoo)
By replacing RFS with EXT4, the ‘sync on fileclose’ problem is removed. The EXT series of filesystems is also more efficient at allocating information into blocks than RFS/FAT32 is. This means less real writes to MoviNAND, which means that the MoviNAND buffer should be smaller, and when a sync is called, fewer commands have to be run. When a sync is called on EXT4, it will still be very slow, as the MoviNAND’s sync is still slow.
Basically, EXT4 improves filesystem grouping which leads to less commands, and does not have the broken ‘sync on file close’ that RFS does. It will not heavily improve sqlite database access in certain apps, as the full fsync on transaction end will still have to go through MoviNAND, and will be slow.
When pulling out the battery, there is a chance to lose data that has been written to a file but has not yet been told to sync to disk. This means that EXT4 is less secure than RFS. However, I believe the performance to be worth the risk.
Loopback EXT2 on top of RFS (OCLF)
By creating a loopback filesystem of EXT2, the ‘sync on fileclose’ problem is removed as well. Since the Loopback File is never closed until the EXT2 is unmounted, RFS will not call fsync when a file in the EXT2 loopback is closed. Since a single large file is created on RFS instead of multiple small files, RFS is unable to mis-allocate the file, or fragment it. The actual allocation of filesystem blocks is handled by EXT2. As a note, care should be taken in making the large file on RFS – it MUST align correctly with the MoviNAND boundries, or operations will be slowed down due to double-disk accesses for files, etc. It is unknown whether OCLF is aligning this correctly (how to determine this? 4KB block size gives double the performance of 2KB block size, so it might be aligning it correctly already).
Loopback also has the benefit of speeding up Sqlite databases (at the expense of a transaction being lost in power outage, as it could still be in ram). As always, this is a performance tradeoff between data security when the battery is pulled out, and performance. When pulling a battery out while using the loopback filesystem, there is a chance to lose the last few seconds of database writes. In practice, this isn’t a huge deal for a mobile phone – most lost data will be resynced when the phone reboots. In my opinion, the performance is worth it because of the very slow speed of a sync on MoviNAND.
Loopback EXT2 on top of EXT4
All of the above for normal loopback EXT2 applies. In addition, when the loopback flushes data, it will be flushed to EXT4 instead of RFS. This will probably be better than flushing to RFS, as the RFS driver is not as well written as the EXT4 driver. The difference should not be very large, though.
Journaling
Journaling on an SSD is not required. Your data will not be lost, your puppy will not die. Here is a post made by Theodore Tso -http://marc.info/?l=linux-ext4&m=125803982214652&w=2
But there will be some distinct tradeoffs with
omitting the journal, including possibility that sometimes on an
unclean shutdown you will need to do a manual e2fsck pass.
Not using a journal is not a big deal, as long as you take care to do a full e2fsck pass when an unclear shutdown has occurred. This is the main reason for a journal – to prevent the need to do a full disk check, and instead the journal can be easily read, and the full disk check avoided.
EXT2 vs EXT4
EXT2 appears to work better on the SGS than EXT4. This is because EXT4 has more CPU overhead than EXT2. Journaling is also very bad on MoviNAND. Why? It appears to be the command buffer in the MoviNAND controller. A call to update the journal will use a command slot in the MoviNANDs buffer, that could otherwise have been used for a real disk write. This means that journaling on MoviNAND is a VERY expensive operation compared to journaling on a ‘dumb’ disk.
Well, you could technically use EXT4 and simply disable the high cpu and other features until you are left with EXT2, since EXT4 and EXT2 are basically the same thing.
At any rate, the difference between EXT4 and EXT2 is not very large, and there’s no need for flamewars over it – it comes down to a choice of ‘running’ performance vs ‘startup’ performance, with EXT2 edging out EXT4 for everyday speed, while EXT4 not required a long disk check at boot.
Future Work
Rewrite the firmware for the MoviNAND’s flash to handle fsyncs properly and not bring the system to it’s knees. I joke, but this is really the true solution.
Other solutions include hacking EXT’s fsync method to return instantly, and ensuring that the real fsync is called when the system shuts down. Or doing nothing, fsync is there for a reason, I guess, and would be fine if MoviNAND’s fsync wasn’t so very slow.
There is probably a lot of small details missing from this writeup. They’ll be updated when we learn more. Thanks for all the useful discussions and arguments, everyone!
Many Thanks to Dennis for this awesome information (officially posted here)
Nice cp, but you could take out everything about movienand, which is not present in g3 we only have onenand...
Ah, and don't forget to give credits or link to op...
FadeFx said:
Nice cp, but you could take out everything about movienand, which is not present in g3 we only have onenand...
Ah, and don't forget to give credits or link to op...
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Click to collapse
Of course Done.
kyrillos13 said:
Of course Done.
Click to expand...
Click to collapse
hi
very useful info for the members very nice of u added to the roll up thread
I don t know why I never read this. Very nice and interesting info.
thank you very much for this!!
What about the link2SDapp? Is this a good choice? I'm using it but think it has probs with the second partition.
Godyn said:
What about the link2SDapp? Is this a good choice? I'm using it but think it has probs with the second partition.
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Click to collapse
Better use app2sd scripts
Thx,
I used it, but it filled my ROM.
What app do you suggest?
I used app 2 SD https://market.android.com/details?id=com.a0soft.gphone.app2sd&feature=search_result
But that didn't solve it.
Hello,
I desperately wish I could use another filesystem (exFAT, NTFS, etc) but I need my external HDD to be readable from my Amazon Fire TV box, Android phone/tablet, and hopefully iOS devices (though the latter is less of an issue if this won't work). From everything I've read, the ONLY file system that can be read by all of these is FAT32. I've tried on my Android phone/tablet using other options like NTFS and even using premium apps, I could get the drive to mount but nothing could be read. I only include this information but I know FAT32 isn't the best option and people will rightfully share that with me but sadly, it's the only option I have in this case.
I also know that while 2TB should be the max that FAT32 can handle, there are several people who have successfully gotten around that. If needed, I can share links to a post talking about that. However, what no one can seem to share is how to actually do that? Do I need to change the disk sector size? I've tried using multiple different software including AOMEI Partition Assistant, EaseUS Partition Master, and MiniTool Partition Wizard, obviously Windows built in (useless), and one or two others whose names escape me at the moment and, although most of them advertise that they can handle FAT32 partitions larger than 2TB, I can find no info on how to actually use them to accomplish this. Is GParted able to do this without problems? Is there any other program that can? Can anyone please share what I need to do to accomplish this? I know I have to have GPT rather than MBR but I don't know what else I need to do.
Thanks so much in advance! I truly appreciate any tips or advice you can share! Take care!!
Open a command window by going to Start, then Run and typing in CMD.
Now type in the following command at the prompt:
format /FS:FAT32 X:
Replace the letter X with the letter of your external hard drive in Windows. Windows will go ahead and begin formatting the drive in FAT32!
Format external hard drive fat32
There seems to also be an issue when using the command line besides the size limit problem. Namely, it can take forever to format the hard drive for some users. Not sure why, but I’ve seen it enough times and it can be very frustrating to wait 5 hours and then have the whole format fail.
As I know the snap-in disk management could not support formating partition from NTFS to FAT 32 when it is larger than 32 GB, if you want do that, you could use some partition software, such as Partition Assistant, GParted, and etc, btw, from your post it mentioned Acronis Disk Director, unquestionable, it is a powerful partition software, however, it need cost too much.
This should be possible with gparted, as long as the sector size of your hard disk is greater than 512 Byte. If not, 2TB will be the limit with Fat32.