[Opinion] Don't Use A2SD/APPS2SD !


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  1. erisuser1

    erisuser1 Well-Known Member This Topic's Starter

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    For those of you who are new to rooting, that's the practical advice I would give you:

    [SIZE=+2]"Don't bother setting up your SD card to use A2SD/APPS2SD"[/SIZE]

    The reasons? It's a bit of trouble, and a problem-maker ... for almost no benefit.

    1) One of the claimed benefits is that you can get more app space. That is "sort of" true, but it may not matter. Most users don't have trouble with lack of space in the /data partition - for them, they gain no benefit for their efforts. (I will admit that a few users - "app hoarders", will run out of space in /data, and for them they need to use A2SD/APPS2SD on 2.1. But most users never find themselves in this situation)

    2) It has been spuriously claimed that A2SD/APPS2SD "improves performance". Unfortunately, there is no hard evidence of this claim whatsoever.

    3) One of it's claimed benefits is that it makes jumping between 2.1 ROMs a little faster, because you do not need to reload apps from the Google market. Yes, that's also true - but leads to problems of its own, too. OTOH, if you are the type of person jumping between ROMs frequently, you are probably want to try a Froyo (Android 2.2) ROM out every once in a while - and they will not boot up with a partitioned SD card.

    That means that every time you want to flip-flop between a previously saved (Nandroid backup) A2SD ROM and a Froyo ROM - and you don't have a spare SD card to use, you will have to backup everything on your SD card to your PC, partition or unpartition, and then restore the SD card. If your card is a nearly-full 8 Gb card, it will take you 90 minutes just for those steps alone.

    I have a bunch of A2SD-enabled ROMs backed up in Nandroid+ext (BDES-) backups - and I am sorry I ever used A2SD/APPS2SD now that I have been using Froyo ROMs. I never needed it for space reasons, and now it makes a pain in the butt to flip-flop between different ROMs saved in Nandroid backups.

    You can use two SD cards if you want; but who wants to synchronize the FAT32 partition between two cards - especially since you will be dropping Nandroid backups in there?.

    And there are ways to fool around with Nand backups (e.g. take the tar file from a Nand+ext backup and put it in a regular Nand backup folder, fix up the MD5 signature file, and then rename the folder prefix from BDS- to BDES- ; or, use the reverse procedure to strip the 'ext' backup from an Nand+ext backup). But really, why?


    Opinions welcome ;)
     

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  2. andrizoid

    andrizoid Well-Known Member

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    i disagree whole heartedly
    ive been on the a2sd bandwagon since tkirton first released it, and had a hand in getting it popularized on the eris roms. its EXTREMELY helpful, especially on sense based roms where your internal memory is already very limited. and like you said, it keeps all of your apps installed when your rom hopping.

    i personally dont care for froyo so i havent had the issue with switching back and forth, but i have a copy of my sd-ext on my computer tha i can easily push back if i have to remove my partition for any reason

    and your coment about it leading to issues-only issues ive ever encountered were with the original versions of darktremor-and that was just trying to get the damn roms setup to use it


    and btw....the froyo built in a2sd is garbage IMO
     
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  3. Peter123

    Peter123 Well-Known Member

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    I think apps/chache2sd is great. My only question that I think was not addressed is:
    what about the sd card reliabity when it is used for frequent read/write and cache operations? I am not sure if these cards are made to operate like like RAMs, hard drives, or SSHDs that are designed for very high number of read/writes at high MFBT

    Peter
     
  4. andrizoid

    andrizoid Well-Known Member

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    i have a script written that automatically backs up my important files on my computer and my sdcard.

    actually only about 20 minutes ago i flashed a new rom to give it shot and got the corrupt sd error. would have been horrible since i had 5 or 6 nandroids backed up, but i ran my restore script and it was all good.

    things mess up, its always good to have something in place in case they do
     
  5. doogald

    doogald Guides Guide

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    I started using a2sd on xtr specifically when I noticed free space was down to the 20 MB range. I'm not sure that I am an app hoarder, but I do have quite a few installed, and, as andrizoid said, Sense based ROMs (and de-odexed ROMs) take up more space.

    I actually do have two SD cards, one for 2.1 ROMs and one for Froyo. And, at this point, I am only going to run one 2.1 ROM (xtr), so there really is no switching back and forth that much between 2.1 ROMs anyway. The only Nandroid backups that I need on each SD are the ROMs that are used with that SD, so the only syncing that I need to do is my Titanium Backup folder. It's a pain, yes, but not all that bad to do every once in a while.

    I also agree that a2sd on Froyo is not implemented well. I have no apps on SD on Froyo at all. The idea that any app that you install goes away for a while when you mount your SD card to your computer is just not a good implementation. The ext3 partition is a far better idea for a2sd. I'd think that Google could provide tools that would allow for the non-destructive partitioning of SD cards if they really wanted to.

    That said, I think that I would discourage a root beginner from installing a2sd unless they were really computer proficient (for example, already could explain to you about multiple partitions on a single computer drive.)
     
  6. andrizoid

    andrizoid Well-Known Member

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    i would discourage a new root user from using anything other than plain jane untill they had all the basics worked out to be honest. too many people dive right into it w/o any bg knowledge...i did when i first got my eris and i ended up stuck on the leak about 10 minutes after rooting because i just had no idea what i was doing :p

    i always recommend fooling around with your phone and adb and all the things that become important later on before you start getting into the more complicated aspects of rooting
     
  7. erisuser1

    erisuser1 Well-Known Member This Topic's Starter

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    Flash memory is not the same thing as DRAM, and is never used for any "performance" related features such as virtual memory management. (It can be used as "swap space" with a partitioned SD card but doing so is generally a really bad idea for a whole bunch of reasons) Gaining additional file system space does nothing for "performance". It is possible that a Class 6 SD card has slightly faster write speed than the system flash in the Eris, but they are probably equivalent in read speed, and all the market apps are dexed into the Dalvik cache anyway - the only time they are ever used is immediately after they are installed (or if the Dalvik cache gets wiped); but that's a read operation, not write. So, again - no performance benefit; only more file system space.

    Different strokes for different folks - a lot of the ROM hoppers seem to like their Froyo ROMs. But, the point wasn't that 2.2 is better than 2.1, but merely that using a partitioned SD card makes the whole process of comparing ROM A to ROM B a much more difficult process than it needs to be (going back and forth between them, that is).

    Exactly my point - avoid all that effort by not partitioning your SD card and using A2SD in the first place if you are getting no benefit by using A2SD.

    The "issues" that I was referring to were:

    - does every kernel support ext3 and ext4?
    - some devs add apps that others don't - and now you have double-installed apps when you bring an ext partition from one rom into another that already has it installed as a system app.
    - some apps which you might have in your ext partition don't play nice on every rom. That's not a problem for an experience dev to figure out, but a how about for a newb?


    I didn't mention that one; for the same reasons, I think that most users won't really need to use that one, either.


    eu1
     
  8. doogald

    doogald Guides Guide

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    I'm not an expert about all of this, but I believe that most of these cards are rated for at least 100,000 write cycles. Remember that all flash memory controllers are pretty smart - they don't necessarily write to the same location with each write; they write the block to another location that gets mapped to the address, so that memory location usage is balanced out to lengthen the lifetime of the card.

    Reading doesn't hurt flash; it's writing that does. If you were worried I'd think about keeping Dalvik cache out of SD. But, think about it; the memory that you are using on your phone is that same sort of flash memory.

    These sorts of cards are used in digital cameras as well, including video cameras, which do a lot of data writes. I think that you can count on these cards lasting through the maximum two years that you'll probably own the phone.
     
  9. erisuser1

    erisuser1 Well-Known Member This Topic's Starter

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    It is writing which wears out flash memory, not reading. There are far fewer write cycles than read cycles - when you are only storing app (.apk) files there.

    Bear in mind that your phone's flash memory - the /data partition specifically, is constantly being written by the phone's live OS.

    Your phones system memory (/data partition, anyway) might just wear out before your SD card - although there is other writing taking place on the SD card (things like browser thumbnails, etc).


    eu1


    PS it is possible that the Eris system flash uses a technique called "wear leveling" which makes the same type of flash memory more robust than another storage medium that does not use wear leveling; I don't know if that is used with SD cards or not.
     
  10. andrizoid

    andrizoid Well-Known Member

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    try letting your internal memory drop below 20 or 30 MB and tell me theres still no performance change :p

    and idk...i guess it can be a hassle when you swith between 2.1 and 2.2 but its not a big enough issue for me to write it off.

    and "all that effort"
    one line,
    adb push *w/e the file name is* /sd-ext
    rather than downloading my 20+ apps each time i flash a new rom...you be the judge :)

    all kernels support ext3, but not many have ext4 support, which isnt really an issue IMO

    ive never run into the issue of having my apps double up, and unless someone can support the claim, i dont think it can happen. have you ever tried to install the same app over the already installed version? it doesnt install 2 of them, one just over writes the other

    and theres not many apps that only work on specific roms...off hand i cant think of any of them that would cause issues on one, and work fine on the other. i believe setcpu was ausing a small issue-or at least it was a little while back, but i think that was something the dev wrote in to avoid rom devs baking the app into their projects
     
  11. andrizoid

    andrizoid Well-Known Member

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    i agree with your comment about the dalvik cache, but thats just my personal opinion and i have nothing to back it up with, but i believe that storing your dalvik cache on your sd can cause some odd issues
     
  12. erisuser1

    erisuser1 Well-Known Member This Topic's Starter

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    "Free memory" is not the same thing as "available file system space", and DRAM is not the same thing as NAND flash memory - they are not used for the same purposes.

    Low "free memory" - as in DRAM - definitely will cause a slow down. But again, Flash memory is not is not DRAM.

    As for sort-of full file systems: they can cause a problem in disk-drive systems because of fragmentation issues, but that is only because disk drives have latency due to (head) seek delay. Flash memory is random access (by page, anyway), and there is no latency by jumping randomly to different page addresses.


    eu1
     
  13. karib

    karib Well-Known Member

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    If you have already moved the dalvik cache to the sd, how would you go about removing it (using the terminal emulator)?
     
  14. andrizoid

    andrizoid Well-Known Member

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    check tkirtons thread. he has all the info there
     
  15. emunny

    emunny Well-Known Member

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    i think apps2sd is garbage and always makes things unstable i love 2.2 roms where u can transfer apps to your sd without partitioning ur sd card
     
  16. Duffman3005

    Duffman3005 Active Member

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    I agree to an extent, it wasn't exactly garbage.

    Though when I use to use 2.1 roms I got a class 4 memory card just so I could move the dalvik over. Once I moved onto 2.2 I couldn't go back, and the a2sd on froyo works just as well as tiki's version imho. Sure, about 60-70% of apps on the market aren't froyo a2sd capable yet, but as Froyo becomes the standard with all the new phones coming out I'm sure that will change. Hell who knows, maybe Gingerbread will have the same improved version of a2sd.
     
  17. bberryhill0

    bberryhill0 Well-Known Member

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    I'm running xtrSense 3.1 with a2sd and have had zero problems. Do I 'need' 80+ apps on my phone? Probably not but they are all right there if I want them. A2sd FTW!
     
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  18. Hypo Luxa

    Hypo Luxa Well-Known Member

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    Again, I think this is just another one of those 'personal preference' options available. I personally use it because frankly, I'm a geek and I have one more 'cool' thing to brag about. Also, I do like the ability to have as many apps as I want, not that I ever will have enough to make a difference, but I have better things to worry about than if one more app is going to be the one that gives me the space warning.

    Besides, being a PC tech, I have it ingrained into my head that OS's like lots of clean space because they hoard resources and I like to give it to them. It's an 8 GB card.. what could giving your apps a small piece of that pie hurt especially given the fact that I'm only using 3GB for other stuff. Kinda seems like I'm wasting 5GB.
     
  19. doogald

    doogald Guides Guide

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    I've had no issues with apps2sd on xtrROM at all. And, unlike Froyo, when you mount your SD card to your computer, you still have access to the apps.

    Froyo's apps2sd is really not well thought-out, for this reason. You cannot have and apps which need to be available at launch, because the the SD card is not mounted until it is too late. May apps with widgets do not work well when they are moved to SD in Froyo.
     

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