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[Q] What are the benefits of formating the sd to ext/swap etc?

I'm a Linux user so I know what swap, ext2, ext3 etc technically means. What I don't understand is what are the *actual* benefits of formating my SD Card to these formats. I've run into a lot of guides and how-tos but no one cares to explain why to do it.
So to sum up:
Does the Android System actually cares if I create these formats?
If it does, will I notice actual increase in performance?
What about apps2SD?
What kind of format do you recomend?
I have an HTC Desire and I'm using CyanogenMod, Oxygen and MIUI in rotation (means I replace one with another every couple months).
Thanks in advance!

aventinus said:
I'm a Linux user so I know what swap, ext2, ext3 etc technically means. What I don't understand is what are the *actual* benefits of formating my SD Card to these formats. I've run into a lot of guides and how-tos but no one cares to explain why to do it.
So to sum up:
Does the Android System actually cares if I create these formats?
If it does, will I notice actual increase in performance?
What about apps2SD?
What kind of format do you recomend?
I have an HTC Desire and I'm using CyanogenMod, Oxygen and MIUI in rotation (means I replace one with another every couple months).
Thanks in advance!
Click to expand...
Click to collapse
Faster SD Card speeds for app2sd, thats mainly it. If you don't use A2SD there isnt much point to it, but if you do it can be very useful. What some people do though are format their System and Data partitions to EXT2 or EXT4 so then the whole system is faster all around and is a large improvement over stock rfs.

fowenati said:
Faster SD Card speeds for app2sd, thats mainly it. If you don't use A2SD there isnt much point to it, but if you do it can be very useful. What some people do though are format their System and Data partitions to EXT2 or EXT4 so then the whole system is faster all around and is a large improvement over stock rfs.
Click to expand...
Click to collapse
Ok so if make an ext partition, the apps that are stored in this partition will run faster. That sounds fair. Should I have both ext and FAT partions? And if I do, how does Android know where to put the apps? Also how about swap?

aventinus said:
Ok so if make an ext partition, the apps that are stored in this partition will run faster. That sounds fair. Should I have both ext and FAT partions? And if I do, how does Android know where to put the apps? Also how about swap?
Click to expand...
Click to collapse
No need for swap, and yes EXT is automatically recognized by android for a2sd, but make sure your ROM supports it. You would have an EXT partition between 256mb-2gb max, and then the rest would be FAT.

fowenati said:
No need for swap, and yes EXT is automatically recognized by android for a2sd, but make sure your ROM supports it. You would have an EXT partition between 256mb-2gb max, and then the rest would be FAT.
Click to expand...
Click to collapse
Ok! That was really eye-opening! Thank you so much!

no problem!

[Q] link2sd vs built in

Ok in FB's kernel thread I asked is link2sd could be creating reboots when linking a app during a automatic update. FB asked why I was using link2sd.
So after some discussion Im confused. And not wanting to clutter his thread anymore Im creating this one.
My understanding is link2sd uses your current ext partition and puts apps in the sxt partition then symbolic links the app to the original location. That way you gain that much space on your internal.
FB says the built in apps2sd of android does that already. But I was told all it does is move the app from the internal to external (sdcard). This is possible even without a ext partition, I know because several people with the Optimus V do not use link2sd or anything like it. They just use the built in app mover.
When I had my Optimus V I used this data2ext but I do not think it would work for our phone since its written for CM7. WIth that my interal memory showed up as however much my ext partition was minus the apps. What it did is trick the OS into thinking the ext partition was really the internal storage.
My question is am I right in how link2sd works or am I misunderstanding?
Is there a version of the data2ext that works on the SGS4G roms we have and I just cant find it?

Here's some reading for you:
http://forum.xda-developers.com/showthread.php?t=919326
bakpinar said:
How it works:
Link2SD mounts the second partition of your SD card as /data/sdext2 and makes OS mounts it at boot time.
When you select an application and press "Create Link" button you can select which files of the application will be linked and moved to SD card. Apk, dex and lib files can be moved and you can select all three or any two of three or even only one of them.
Depending on what you select, Link2SD moves apk file, dalvik-cache (.dex) file and lib files (.so) to SD card's second partition and creates symbolic links in original directories.
Click to expand...
Click to collapse
apps2sd does NOT require repartitioning your sdcard and it's an Android 2.2+ feature.
links2sd requires your sdcard to have at least 2 partitions + formatting your sdcard, and is a 3rd party application.

Ok I understand that. Don't we need a ext partition anyway? IM trying to wrap my head around this but I'm still confused how the built in moves the app to the ext partition.
I'll read more of that thread tomorrow stupid ISP OS doing maintenance and my net is crapping out.
Vroom Vroom

First of all, what do you mean by "ext partition"?

FBis251 said:
First of all, what do you mean by "ext partition"?
Click to expand...
Click to collapse
I think what eollie is looking for is what we had on Froyo. Remember dsexton's ext4 guide? We could create a second (ext4) partition on our EXTERNAL Sdcard and use Link2sd to move apps there..
On Froyo I had a second 1.5 GB ext4 partition on my EXTERNAL sdcard and used Link2sd app to move my apps to that partition. It worked Great and I miss having it on Gingerbread. I could not get dsexton's guide to work on Gingerbread at all. It caused me all kinds of problems. Even soft bricks..
Sorry if I'm wrong eollie.

On my old Milestone xt720 I used link2sd primarily before 2.2 was available for the phone. It involved setting up an ext4 partition as well as a linuxswap partition.
At this point ... seeing as we have gingerbread which already moves most apps to sd card ... the only advantage I can really see is that when you use links2sd you can move absolutely any app to sdcard (keyboards, alarm clock, ect) that would not normally be moved.
Now one thing to be cautious about when using links2sd is some apps will not work properly when on the sd card. This is especially true with apps that have widgets. For example - if you move your digital clock to sd card the clock widget will not display.
I don't know if this will be helpful but I just thought I would offer my input.

Jerry D said:
I think what eollie is looking for is what we had on Froyo. Remember dsexton's ext4 guide? We could create a second (ext4) partition on our EXTERNAL Sdcard and use Link2sd to move apps there..
Sorry if I'm wrong eollie.
Click to expand...
Click to collapse
You are correct.
The link I posted is what I used on my Optimus V. It tricked the phone into thinking that partition was the internal memory.
Like jiggleynuts (that name kills me) said you have to be careful with what apps you put on the sdcard. I was using that but when I update apps it would move them to the sdcard if they could be. And my apps that have widgets I use were breaking cause of it.
Again if we can use something like the data2ext I linked to then I would scrap link2sd faster than you could blink. I hate having to use a app when there is a alternative like the data2ext stuff.
Am I wrong in thinking the ext support we have is the same as what the op in the thread I linked is talking about?

eollie said:
Ok in FB's kernel thread I asked is link2sd could be creating reboots when linking a app during a automatic update. FB asked why I was using link2sd.
So after some discussion Im confused. And not wanting to clutter his thread anymore Im creating this one.
My understanding is link2sd uses your current ext partition and puts apps in the sxt partition then symbolic links the app to the original location. That way you gain that much space on your internal.
FB says the built in apps2sd of android does that already. But I was told all it does is move the app from the internal to external (sdcard). This is possible even without a ext partition, I know because several people with the Optimus V do not use link2sd or anything like it. They just use the built in app mover.
When I had my Optimus V I used this data2ext but I do not think it would work for our phone since its written for CM7. WIth that my interal memory showed up as however much my ext partition was minus the apps. What it did is trick the OS into thinking the ext partition was really the internal storage.
My question is am I right in how link2sd works or am I misunderstanding?
Is there a version of the data2ext that works on the SGS4G roms we have and I just cant find it?
Click to expand...
Click to collapse
eollie -
did you ever get the data2ext mod working for the t959v?
i remember you from the optimus v forums last year.
correct me if i'm wrong but we used the data2ext mod with bumblebee and harmonia? i'm considering trying that data2ext v7 mod on this device. i'm actually really surprised that mod isn't being used with this device like it was with the O-V. Both have limited internal memory. maybe i've not learned enough about this device and it isn't capable of utilizing the mod. i'm kinda curious why darktremors app2sd mod isn't used either. its an easy option in the kitchen. either way i'm curious what you've found out or experienced with these mods. i do know link2sd works with this device, so i'm assuming data2ext and darktremor app2sd would too.

I replied to your pm. But Ill answer here too, I never found a conclusive answer. So I just move apps using the built in android app2sd function. If there happens to be a app that needs images loaded at boot like launcher themes or the such I just move it to internal memory.

ok cool. i may try it. i dunno.
thanks for your response.

[Q] SD-EXT on SGS4G with CM9?

I'm currently running bhundven's herring CM9 with no kernel modifications and CWM 6. I find that the internal storage for this phone is very low and only holds a small amount of applications, especially since many apps seem to not want to install at all (about 3/4 of the time I try to install things, I get either "Package invalid" or "Insufficient space available", which is extremely annoying and might be a separate problem).
Is there any way that I can get sd-ext to work on this phone with this setup? I'd rather not switch kernels (I'd love to get TWRP recovery but the flashable doesn't work for me and I don't want to switch kernels).

cpkelley94 said:
I'm currently running bhundven's herring CM9 with no kernel modifications and CWM 6. I find that the internal storage for this phone is very low and only holds a small amount of applications, especially since many apps seem to not want to install at all (about 3/4 of the time I try to install things, I get either "Package invalid" or "Insufficient space available", which is extremely annoying and might be a separate problem).
Is there any way that I can get sd-ext to work on this phone with this setup? I'd rather not switch kernels (I'd love to get TWRP recovery but the flashable doesn't work for me and I don't want to switch kernels).
Click to expand...
Click to collapse
I haven't used it but this app should do the trick.
https://play.google.com/store/apps/details?id=eu.codlab.int2ext
Let me know if it works.

I prefer Mounts2SD, which lets you completely configure things. I was running PACman with cache and dalvik offloaded which worked quite well. And free is a good price.
https://play.google.com/store/apps/details?id=com.spazedog.mounts2sd

That seems like it just switches the internal and external storage, not making an ext partition on the SD card. But can things like this really be done through an app? I thought these things had to be done through init.d or build.prop scripts.
Sent from my SGH-T959V using xda app-developers app

The app creates an init file. Or so it appears. Like I said I don't use it. It seems that raze does and I'd defer to him here. Either his app or the one I linked should work fine.

Thanks (given) to both of you. And any ideas on what else might be causing the invalid packages when downloading from the play store? It happens even though I have much more free app space than I would need (eg. I had 119 MB of free space and a 30 MB app download failed).
EDIT: Just tried using Mounts2SD, but it couldn't find the sd-ext partition. Do I need to create that manually, and how?
Sent from my SGH-T959V using xda app-developers app

Titanium backup had a feature to integrate app updates into the Rom.
Sent from my SAMSUNG-SGH-I547 using xda app-developers app

Another way is to create ext4 partition (about 1G is usually enough) on you SD card with free MiniTool Partition Wizard and then use Link2SD to link apps/dalvik to this partition. I've been using it like this for a long time and it works fine. There are plenty of guides on the Web how to do that.

I used CWM or TWRP to create the sd-ext partition. You need to create that first somehow... if MiniTool Partition Wizard will do it without wiping the sdcard, that's better than recovery though.
My method was boot to recovery, mount sdcard, copy everything to computer HD, unmount sdcard, partition sdcard with 2 GB sd-ext (because I wanted lots of space, but I'd probably cut it down to 1 GB next time), mount sdcard, copy everything back from computer HD, unmount sdcard, reboot to system. Then launch Mounts2SD, pick what format you want the sd-ext in (FAT or ext2 are the fastest, but you can take ext3 or ext4 if you're not going to just disable the safety features) and what stuff you want moved over.
Edit: Just found this link, which I haven't used but which explains how to do the sd-ext with MiniTool... apparently MiniTool DOES still wipe the partitions though, so you may as well just use CWM/TWRP and make your life easier.
http://forum.xda-developers.com/wik...#using_MiniTool_Partition_Wizard_Home_Edition

Theraze said:
I used CWM or TWRP to create the sd-ext partition. You need to create that first somehow... if MiniTool Partition Wizard will do it without wiping the sdcard, that's better than recovery though.
Click to expand...
Click to collapse
MiniTool will wipe the sd card to create the new partition as well. I wish there was a way to do it without wiping the card but there is not. So back that stuff up first.

Madein Cyberspace said:
MiniTool will wipe the sd card to create the new partition as well. I wish there was a way to do it without wiping the card but there is not. So back that stuff up first.
Click to expand...
Click to collapse
I used GParted to partition my SD card. NO WIPING. Move, resize, add partitions.

nevkuril said:
Another way is to create ext4 partition (about 1G is usually enough) on you SD card with free MiniTool Partition Wizard and then use Link2SD to link apps/dalvik to this partition. I've been using it like this for a long time and it works fine. There are plenty of guides on the Web how to do that.
Click to expand...
Click to collapse
Yes, but our herring kernel does not support EXT4 partition, I tried it myself
and it didn't work. I had to create EXT3 which is supported by almost all kernels.

Eh, my results varied. Worked fine for me with ext4. And worked fine for my wife as well.

Rebel_X said:
Yes, but our herring kernel does not support EXT4 partition, I tried it myself
and it didn't work. I had to create EXT3 which is supported by almost all kernels.
Click to expand...
Click to collapse
The OP says he's running CM9. That's what I'm running but I use Proton kernel as CM9 kernel has a video bug, and ext4 partition works just fine for me. Strange if Bryan really removed ext4 support, it's just a line in the config file.

Successfully made the partitions last night but my phone won't mount the SD card anymore. Was trying ext3, I'll try ext2 and ext4.
EDIT: Fixed the problem, changed my partition to ext2 and set both partitions to "Primary" (not sure which one did the trick).

cpkelley94 said:
Successfully made the partitions last night but my phone won't mount the SD card anymore. Was trying ext3, I'll try ext2 and ext4.
Click to expand...
Click to collapse
Make sure that you make the first partition Primary/FAT32. This will be your normal SD card. Just take about 1GB of space from it at the end. Then make second partition Primary/ext4 with size to the end of the card. You can try ext2/3 but I don't think it is really necessary.

MiniTool will NOT wipe your partition if you do it right.
dsexton had a guide posted on how to do it.

Is it worth making a swap partition? If I remember correctly it significantly degrades the life of the SD card (and microSD's are delicate as it is), and I don't know if it would significantly increase performance.

cpkelley94 said:
Is it worth making a swap partition? If I remember correctly it significantly degrades the life of the SD card (and microSD's are delicate as it is), and I don't know if it would significantly increase performance.
Click to expand...
Click to collapse
I also created 128MB swap partition, not supported too and not mounted.
I tried to used swapper2 app from the market, but it says not supported by
kernel. Now I lost that space till I feel motivated to format or repartition the SD
card again.
I am using hefe kernel btw on AOKP milestone 6-5.

No swap.
Sent from my SGH-T959V using xda app-developers app

[Q] Can't move apps with Link2SD

I have tried to move apps to sdcard with Link2SD and other similar apps. It fails and says that I can't move them because my device has a primary external storage which is emulated from the internal storage.

Here is a screenshot of the message

Howdy!
as far as I have found out (and been following this problem on and off since I got my plus a few months ago) there is no proper way to move apps to your SD card. Best solution (and the one I am using) is to partition your SD Card then use Link2SD to link apps on your SD. You can set it up to do so automatically for every new app you install. As for partitioning I found this guide the best since I'd never attempted it before but it works really well.
http://forum.xda-developers.com/showthread.php?t=2126363
Good luck and hope this helps a little!

Thanks a lot

lance2355 said:
Howdy!
as far as I have found out (and been following this problem on and off since I got my plus a few months ago) there is no proper way to move apps to your SD card. Best solution (and the one I am using) is to partition your SD Card then use Link2SD to link apps on your SD. You can set it up to do so automatically for every new app you install. As for partitioning I found this guide the best since I'd never attempted it before but it works really well.
http://forum.xda-developers.com/showthread.php?t=2126363
Good luck and hope this helps a little!
Click to expand...
Click to collapse
Do we need to root phone for that?
If yes then what's the point of making partitions.
Sent from my GT-I9105 using xda app-developers app

fayez107 said:
Do we need to root phone for that?
If yes then what's the point of making partitions.
Sent from my GT-I9105 using xda app-developers app
Click to expand...
Click to collapse
Well, my phone was rooted anyway but I think Link2SD needs it. As to why exactly it needs to be partitioned I can only tell you that when my card wasn't partitioned as suggested in the guide I linked then Link2SD wouldn't even offer to link the apps. I am no expert as I pointed out but this was a solution that worked for me. It may well be someone else found something better that doesn't require partitioning. To my knowledge doing things this way requires root AND the partitioned SD card.

lance2355 said:
Well, my phone was rooted anyway but I think Link2SD needs it. As to why exactly it needs to be partitioned I can only tell you that when my card wasn't partitioned as suggested in the guide I linked then Link2SD wouldn't even offer to link the apps. I am no expert as I pointed out but this was a solution that worked for me. It may well be someone else found something better that doesn't require partitioning. To my knowledge doing things this way requires root AND the partitioned SD card.
Click to expand...
Click to collapse
Did you try Apps to SD? Ill be rooting very soon and see what happens. If none works then last stop would be to make partition.
Okay I did root my phone successfully. Still cant move apps. Now going to do this partition system. Hope it works !

fayez107 said:
Did you try Apps to SD? Ill be rooting very soon and see what happens. If none works then last stop would be to make partition.
Okay I did root my phone successfully. Still cant move apps. Now going to do this partition system. Hope it works !
Click to expand...
Click to collapse
Yeah, I tried Apps to SD as well but without success. You get exactly the message as the OP said here http://forum.xda-developers.com/showpost.php?p=42863865&postcount=2
Same goes for Link2SD however once you partitioned it at least offers you to link the apps. But like I said that only happened after I did the partitioning. Beforehand it would not even offer that.
I am not entirely sure what or why Samsung did what they did in kinda blocking the moving of apps to an external card but it it really blows considering that you only get a somewhat limited amount of storage to begin with.

lance2355 said:
Yeah, I tried Apps to SD as well but without success. You get exactly the message as the OP said here http://forum.xda-developers.com/showpost.php?p=42863865&postcount=2
Same goes for Link2SD however once you partitioned it at least offers you to link the apps. But like I said that only happened after I did the partitioning. Beforehand it would not even offer that.
I am not entirely sure what or why Samsung did what they did in kinda blocking the moving of apps to an external card but it it really blows considering that you only get a somewhat limited amount of storage to begin with.
Click to expand...
Click to collapse
Hello again brother. Same here. Before partitioning there was not any option to create link even.
I did the partitioning stuff did work. I can successfully transfer my apps into the ext2 partition i created. (Btw which partition format did you go with?)
How ever I believe folder mount is still a better option as it does not require you to create partitions and works directly such as you enter a brand new card without partition and move apps into card and then it links it. But the only drawback is you need to purchase the app :

fayez107 said:
Hello again brother. Same here. Before partitioning there was not any option to create link even.
I did the partitioning stuff did work. I can successfully transfer my apps into the ext2 partition i created. (Btw which partition format did you go with?)
How ever I believe folder mount is still a better option as it does not require you to create partitions and works directly such as you enter a brand new card without partition and move apps into card and then it links it. But the only drawback is you need to purchase the app :
Click to expand...
Click to collapse
I used ext4 for my partition. And I hadn't heard of Folder Mount until you mentioned it. Will have to check it out. Can you actually move stuff if you use that?

lance2355 said:
I used ext4 for my partition. And I hadn't heard of Folder Mount until you mentioned it. Will have to check it out. Can you actually move stuff if you use that?
Click to expand...
Click to collapse
Well ext4 didn't work for me idky though ext2 did and it worked. But creating partitions is pure junk and it would reduce the life and speed of your card (its something i believe) so I deleted the partitions and brought my card into original format.
And yes man Folder Mount is something we need ! It does exactly what both of us want. Simply move all the app data from internal memory to external memory and as soon as you move you have empty space on your internal storage and external storage is occupied. Its simple and very clear and easy to use. Just 3 clicks i believe and its done. And another good stuff is it will show you how much an app is occupying internal space and then moves it into SD card and also doesn't show important system apps to move as moving them creates problem.
There's a free version to try which would allow you to move 3 apps only and if you want more then buy the app for 2 Dollars.
Its developed by @madmack. Do check it out. The sad part for me is I dont have a credit card nor Paypal is available in my country
And i need this app badly !

[Q&A] 2 GB External Data -- Hefe Hook Kernel and others

The Hefe Hook kernel allows you to mount a partition of your microSD as /data, getting 2 GB (or more) for your apps and their data.
Please ask your questions here about installation, use, or general approach.

This is great @jeffsf and can u show me how to re-partition the "real internal" storage? I mean expanding the /system since u put the /data out of it. Thanks man
Sent from my GT-N7000 using Tapatalk 2

daothanhduy1996 said:
This is great @jeffsf can u show me how to re-partition the "real internal" storage? I mean expanding the /system since u put the /data out of it.
Click to expand...
Click to collapse
Yes, you've hit on another of the reasons I've been exploring using the microSD for "live" storage. It's one thing to use potentially slow storage for photos that you basically write once or "app to SD" where you read the APK at boot time, make sure your ODEX in the Davlik cache is good, then generally read from the internal-flash cache. It is another when that memory is being read and written "constantly" when your phone is running.
The good thing is that once /data is not part of the internal flash filesystem, you don't have to worry about one ROM (kernel) thinking it begins at one place and another saying it starts at another. Previously, if one ROM had one /system size and another and a different one, the next partition, /data, would look to be corrupt when you swapped ROMs.
As a warning, not all users have fast microSD cards. Some that say "Class 10" on them really are dogs, especially for small reads/writes. The "Class" ratings are for sustained writes, as you would have with a camera recording video. If your ROM is "external /data" only, or even defaults to that, be prepared for a slew of "Your ROMs sucks. It is so slow." complaints.
You'll also need a way to automate formatting the card. It can be done on the phone, as long as you aren't trying to preserve any data.
As I recall, the layout of the MTD partitions is done in drivers/mtd/onenand/samsung_galaxys4g.h I would be careful not to move the partition boundary for efs, as you'd have to move the data it contains in your updater script. Repeating the warning about not moving the boot and recovery partitions is probably a good idea as well!
Your build tree may need some of these values, or at least think it needs some of these values. For example, device/samsung/aries-common from the CyanogenMod/cm-11.0 (KitKat) branch calls out NAND page sizes, partition sizes, and flash block sizes. I haven't looked in detail at your build tree so I can't comment on how it might handle things differently than the CyanogenMod one.

itzik2sh said:
Hi
I hope I don't ask anything silly, but please let me know if any of my assumptions is wrong :
1. I take FBi's251's AOKP milestone 6 (ICS 4.0.4)
2. 8GB SDCard was formatted to FAT32 (4GB) and EXT3 (4GB) using TWRP kernel
(Beastmode's proton kernel to be exact).
3. I would flash this kernel and it would move apps and their data to the sd-ext
without any special additions.
Thanks. I read the thread, but unfortunately 8GB SD is what i have and I think it should be enough.
Thanks again.
P.S - it's for 2 guys I already sold them my SGS4Gs. I want them to be happy...
Click to expand...
Click to collapse
AOKP should be fine. I haven't tried it recently, but it was the tree in which I did the early Hefe Kernel development.
As I understand it, you have a microSD with
partition 1: 4 GB FAT32
partition 2: 4 GB ext3
So that can work, but will need some tweaking of the init-on-fs.sh script. I intentionally didn't use the second partition as so many scripts gobble that up as sd-ext and do who knows what to it.
My first preference would be to reformat the cards, perhaps:
6 GB FAT32
1 MB ext2/3/4 (Yes, 1 MB, a sliver, choice of ext2, ext3, ext4 up to you)
2 GB ext4
since then the script will work without modification and if they install a third-party script that uses the second partition, it won't corrupt their data.
If you were to keep the formatting the way that it is now, you'd need to edit the mount commands in the script to look something like:
Code:
/system/xbin/busybox umount /data
/system/xbin/busybox mount -t ext3 -o noatime /dev/block/mmcblk0p2 /data
(removing the sd-ext mount)
I'm not sure what your expectations are, but all that the kernel and that script will do is mount a different disk partition on /data -- you need to manually move the data over (or restore from something like Titanium Backup). There may be some trickery in renaming that could be used with TWRP backups to restore from data.yaffs2.win to the new /data partition, but I haven't tried that at all.

Hi Jeff
Thanks for your quick reply, and sorry again for not seeing the Q&A thread.
I think making it :
partition 1: 4 GB FAT32 (sdcard)
partition 2: 2 GB ext3 (sd-ext)
partition 3: 2 GB ext3 (data)
partition 4: 1 MB (spare)
would be better and handle data as well. don't you think ?
Would it be worth doing with a "Team" micro-SD card (class 6 I believe) ?
Thanks.

I haven't tried a Class 6 card, but my gut feeling is that it will be dicey. I didn't "commit" to using /data on microSD until I had tried it for several days using Titanium Backup's ability to move both apps and app data to the external card. I would try that first, especially as the phones in question aren't going to be in your hands (I consider you an expert user, able to manage things outside the UI with ease).
I've attached some testing I did a while ago with Transcend and SanDisk cards. When you look at them, realize that the speed scale changes between them. I have a feeling that the real "performance" on a device is going to be related to relatively small reads and writes, not the ability to stream video to the card. I also don't know much about the Team brand, but I found that even some well-known brands didn't have the performance of the Transcend or SanDisk in the same category.
However you configure your cards, I would definitely recommend a journaling filesystem of some sort. I've had my microSD come loose inside the phone. The journal will at least help to reduce any filesystem corruption should that happen.
You don't need the fourth partition -- I have it there to be able to keep rsync backups for fast ROM swapping.
.

Regarding the apps data, have you tried exploring the Mount2SD script ?
sent from me

I've tried a couple of the scripts out there in the past. Since backing up my data is very important to me, I trust the scripts in Titanium Backup to work well with its backup/restore strategies.
Mounts2SD looks like it has gotten a lot more sophisticated than it was when I tried it in the past. It sounds like something worth trying in its current state. At a quick glance (and not looking at the code), I'd personally make some different choices about features; enabling journaling, and being concerned about why lost+found was filling up (things should only appear there if the file system is found to be corrupt).