is ext2 or 3 the only choice for SD card?

[kopsis]

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]

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)

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.

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.  

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]

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)

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