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Full Version: is ext2 or 3 the only choice for SD card?
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macwiz
I'd like to install things to my 64MB SD card, but I understand that FAT is just no good for installing applications on with the pdaXrom. Unfortunately my SD card is a SanDisk that works well as FAT but is hopeless when formatted ext2 or ext3. Are there any other formats I could try that it might behave better with and that I could install applications on?
macwiz
Err, I take it that's a 'no' then.

Ah well.

Still, for any one who hasn't got money to burn on hi-capacity SD cards that might not work, it cheered me up no end when I stumbled upon the installer options for the pdaXrom that allow you to make the root partition 121 mb instead of 50 mb. Brilliant work! Now I can put my apps on the internal drive, and use the SD for storage (because it works fine when formatted FAT). Still like to know if there are any alternatives that will work though.

Thanks
pgas
I think the main problem with FAT is that you can't make symbolyc link.

Here is a thing you can do, this is a diy solution and requires some hand works :

- install the applications on the internal flash
- move some files (not symbolic links ;-)) to the sd card. (you can use ls -l and symbolic links will be marked with a l at the begining of the line
- use ln -s /mnt/card/myfyle /original/path (you can consider ln -s is working like cp and link entire directory)

This is perhaps not the greatest solution, but this way you can transfer some kb to your sd.

(I still don't understand the problem with the 50mb root partition, except
that you must be a bit more careful, if you have a 50 mb partition, just install to /home/user or /mnt/user and apps will go in the other partition
macwiz
I guess I might appreciate the other places to install apps more if I knew how much space I had on them. Is there an equivalent to diskfree? Or a command that returns free space values?
blakeyez
QUOTE
Is there an equivalent to diskfree?


CODE
df -h


should do the trick.

Dave
offroadgeek
QUOTE(macwiz @ Oct 31 2004, 10:49 AM)
Unfortunately my SD card is a SanDisk that works well as FAT but is hopeless when formatted ext2 or ext3.

that's odd... I have several sandisk SD cards, and I keep my 256mb Sandisk SD card always in my pdaxrom 760 formatted as ext3... with no issues.

what specific errors/issues do you get when formatting your SD cards to ext2/3?

edit: I take that back... I've actually been using ext2 with my SD cards... but still no problem with that
rgrep
You could also try UMSDOS. I'm not sure if pdaXrom supports it but it allows you to have a Linux filesystem layer on top of a FAT-formatted disk. It supports everything a standard Linux filesystem does (e.g. long filenames, symbolic links, permissions).
macwiz
The SD card I have is a 64MB sandisk. It appears to format fine. I install apps to it, and they appear to install fine. They work for a while. Then all of a sudden they don't. I unmount the card and do an e2fsck, and then one of 2 things happen. Either I am told there is an invalid superblock and I should try an alternate superblock option (which I do and get the same error). Or I can fix the filesystem, but only if I use the -y option, because the fixes scroll up the screen forever. Once it has done its work I mount the SD and still nothing works.

I never get a problem with a fat format.

Will look into the UMSDOS format. Might be a while though.

Thanks
richardh
I am in a similar situation with a 1gb card that works fine as fat32, but am reluctant to format ext2/3 given the issues many have had so I have been using it for bulk storage only. Your post made me start thinking about options and here is what I found works. Use a loopback mount to utilize space on your "safe" fat32 partition as ext2/3

Steps:

1) Create space to be mounted as ext2/3. Example is 100MB where ext2.img is on your SD card
# dd if=/dev/zero of=ext2.img bs=1024 count=102400

2) Format as ext2 (or 3...)
# mkfs.ext2 ext2.img
mke2fs 1.34 (25-Jul-2003)
ext2.img is not a block special device.
Proceed anyway? (y,n) y

3) Create a mount point
mkdir /mount

4) Mount file as filesystem
# mount -o loop,rw -t ext2 ext2.img /mount/

Seems to work fine... no ext2/3 formating risk to your SD card and all of the benefits of a real unix filesystem.

-Richard
scoutme
interesting... I'll keep it in the golden hints smile.gif
going to use it if any prob occurs.

What do you find in the so used fat32 if you navigate it from a windows box?
richardh
Just a big file, nothing special about it really.
henrysviper
I was thinking about the ext2-in-a-file solution too, but I was curious about the performance penalty due to this indirection. Richardh, could you please perform some simple benchmarking for us? (Thank you for the detailed instructions by the way).
kopsis
I'm loop mounting an ext2 filesystem image for running Python from an SD card and I really don't notice any performance degradation from the loop overhead. SD card bandwidth on the Zaurus is the bottleneck so adding a little CPU overhead for the indirection really doesn't hurt anything.
anunakin
ext 3 need more CPU calls, for a bit of util thinks for a PDA... use ext2... is the better choice for SD/CF...
Zumi
QUOTE(anunakin @ Nov 24 2004, 03:20 PM)
ext 3 need more CPU calls, for a bit of util thinks for a PDA... use ext2... is the better choice for SD/CF...

But pdaXrom likes to freeze sometimes and then you have to fsck the whole ext2 partition, maybe you lose files, partiton integrity. Ext3 restortes the state before-freeze in 1 sec while booting.

So I think ext3 is far better, but not for performance reasons. I haven't done any performance test with them however, so I don't know what is the speed difference.

Zumi smile.gif
kopsis
QUOTE(anunakin @ Nov 24 2004, 06:20 AM)
ext 3 need more CPU calls, for a bit of util thinks for a PDA... use ext2... is the better choice for SD/CF...

It just so happens that yesterday we got benchmarks for the same 1GB card formatted as ext2 and as ext3. The numbers show that there's only a tiny decrease in write performance with ext3 and the read performance was actually better (though the actual difference is probably statistically insignificant).

The SD interface on the Zaurus is just so slow and uses so much CPU that the added overhead of ext3 really doesn't hurt anything. And on removable media, a journaling filesystem like ext3 is a pretty good idea from a filesystem integrity point of view. The only compelling reason not to use ext3 is that the jounal may consume too much space on small memory cards.
msjones
I just bought a 512mb sd card and was wondering how to utilize some of it for linux file system and still have windows read and write to it. It sounds like your solution is a winner! I have three questions, I hope you can answer them. I'm a little new to linux so I'm trying to get this straight to avoid damaging my new card. I'm running oz on a 5600.

1) Would I issue these commands from /mnt/card/ (cd /mnt/card/)?

2) If I want to allocate 200mb to the ext2.img, would the following line be correct?
# dd if=/dev/zero of=ext2.img bs=1024 count=204800

3) Is it safe to move /opt and /home to this ext2.img?

Thanks for your help!
Mark
pgas
QUOTE
1) Would I issue these commands from /mnt/card/ (cd /mnt/card/)?


yes for the steps 1 an 2 for the steps 3 and 4 it doesn't matter. (And I think for steps 1 and 2 it wouldn't matter if you use /mnt/card/ext2.img instead of just ext2.img)

QUOTE
2) If I want to allocate 200mb to the ext2.img, would the following line be correct?
# dd if=/dev/zero of=ext2.img bs=1024 count=204800


I think it you are correct.

I think bs is in byte and count specify the number of blocks of bs size, so in this
case it would create a 1024* 204 800 byte image file. (I think the original exemple creates a 100MB file and not a 10 MB file).

Be aware that this takes some time.

QUOTE
3) Is it safe to move /opt and /home to this ext2.img?


For this you would need to check if there is something in opt or home (or ask in a forum where people use the sharp rom) that is required to mount the image, because if it is the case then you won't be able to mount the image after a reboot....

Perhaps you could simply uninstall some apps and reinstall them in the new mounted image. I think you will take advantage of your partition this way with no risks.

Some problems of this method are:
1) you canno't resize the file afterward
2) if the big file is corrupted you are likely to loose 200MB of data (make backup often)
technojunkie
If/when you can afford it I would highly recommend finding an SD card that works with Ext2/3.

I fought with a standard lexar card for a year and was always Fscking it, I decided it was time for a change and bought a new card, It didn't work so I took it back and tried a different brand until I found a working card. It was a P.I.T.A as it took a couple days per card to find out I couldn't use it, but I haven't had any trouble now for 3 months.

And if you still want to be able to read the card on a windows box there are programs available that make windows read Ext2.
diesel1
Hello,

I always use Integeral SD cards, any format, particularly EXT2/3, EXT3 with pdaXrom but only EXT2 with pdaXrom and DoH!

DOH!


Anyhow, use what you want. smile.gif

Simon.
rgrep
Another option to allow both ext3 and a FAT filesystem for Windows/flashing is to partition your card. I have split my 512MB SD into two - partition 1 is 135MB for NAND backups and flashing, and partition 2 uses the rest of the space and is ext3 for general use. I haven't performed any benchmark tests but it would be interesting to see if this gives you performance benefits over using an ext3 fs-image file stored in a FAT fs.
grog
QUOTE(richardh @ Nov 3 2004, 01:36 AM)
1) Create space to be mounted as ext2/3. Example is 100MB where ext2.img is on your SD card
# dd if=/dev/zero of=ext2.img bs=1024 count=102400

2) Format as ext2 (or 3...)
# mkfs.ext2 ext2.img
mke2fs 1.34 (25-Jul-2003)
ext2.img is not a block special device.
Proceed anyway? (y,n) y

3) Create a mount point
mkdir /mount

4) Mount file as filesystem
# mount -o loop,rw -t ext2 ext2.img /mount/

All goes well for me except for the last step (mount)

QUOTE
root@poodle:/mnt# mount -o loop,rw -t ext3 /mnt/card/ext3.img /mnt/img/
mount: Mounting /mnt/card/ext3.img on /mnt/img failed: No such device

I tried it first with ext3 then with ext2. The /mnt/img directory exists. Any idea what gives? thks
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