SD users with ext2 FS: please share your experiences!

[gcf]

Some more thoughts on filesystems details:

What block size would be useful for certain type/size of Flashs?

Does it make sense to map them at the same size (as suggested in JFFS2) ?

If i read it correct, JFFS2 does automatically re-locate badblocks when detecting a write error, how do ext2/3 or VFAT perform? So far ein know, they only handle badblocks when specifically told so, which might account for a number of the observed problems here.

On the other side - SD cards do have wear-levelling, do they also have automatically relocation transparent to Z? I searched the net, but could not find any reliable note on this, just that "SD have ECC ... data are corrected before written back to host".
That does not sound like relocation, just ECC.

Reason is:
Especially for journalling a log wandering through a badblock might be very nasty.

Now JFFS2 (3) would be perfect to adress this problem, but when used for SD  - does it still make sense?

For all that different things to consider - a selection matrix would be nice:
(other things to consider is interoperability of course)

filesystem/card | vfat | ext2 | ext3 | jffs2
CF
MMC
SD
microdrive
(int. Flash?)

[kopsis]

On the other side - SD cards do have wear-levelling, do they also have automatically relocation transparent to Z? I searched the net, but could not find any reliable note on this, just that "SD have ECC ... data are corrected before written back to host".
That does not sound like relocation, just ECC.
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See [a href=\"http://www.sandisk.com/pdf/oem/WPaperWearLevelv1.0.pdf]this whitepaper[/url]

SD and CF both have controllers that do a significant amount of abstraction between the logical operation requested by the host and the physical operations performed on the actual flash. On top of that, each vendor's controller behaves differently as they all make different trade-offs between cost, speed, and reliability.

[gcf]

On the other side - SD cards do have wear-levelling, do they also have automatically relocation transparent to Z? I searched the net, but could not find any reliable note on this, just that "SD have ECC ... data are corrected before written back to host".
That does not sound like relocation, just ECC.
[div align=\"right\"][{POST_SNAPBACK}][/a][/div]

See [a href=\"http://www.sandisk.com/pdf/oem/WPaperWearLevelv1.0.pdf]this whitepaper[/url]

SD and CF both have controllers that do a significant amount of abstraction between the logical operation requested by the host and the physical operations performed on the actual flash. On top of that, each vendor's controller behaves differently as they all make different trade-offs between cost, speed, and reliability.
[div align=\"right\"][a href=\"index.php?act=findpost&pid=85772\"][{POST_SNAPBACK}][/a][/div]

Thanks for that informations.

I read it that way, that the card uses some internal storage to remember the sector-mappings between logical an physical location.
So indeed JFFS2/3 is trying to do something not really required - additional wear-levelling (simply wasting cpu, though compression of files might speed things up a bit).

When the internal mapping-logic of the flash is flawed any filesystem get screwed up totally.

So what filesystem to use? vfat no links, loopbacked-ext2 on vfat a waste of cpu (and putting a dangerous additional level of potential failure in), native-ext2 at least sometimes failing, ext3 certainly too, confusing...

[kopsis]

So what filesystem to use? vfat no links, loopbacked-ext2 on vfat a waste of cpu (and putting a dangerous additional level of potential failure in), native-ext2 at least sometimes failing, ext3 certainly too, confusing...
[div align=\"right\"][a href=\"index.php?act=findpost&pid=85808\"][{POST_SNAPBACK}][/a][/div]

In my experience, the choice of SD card brand (an even model) is far more important than filesystem. The problems most folks experience with SD cards have nothing to do with flash wear. It's a well established fact that compatibility between SD cards and the interfaces on mobile devices leaves a lot to be desired. Ask owners of older Dell PocketPCs about SD compatibility and you're likely to get an earful

I've found that SD cards that work reliably in the Zaurus do so regardless of which filesystem you choose. Cards that don't will eventually have problems regardless of the selected filesystem. Now, the more complex the filesystem, the sooner an unreliable SD will exhibit problems. That's the reason some folks get by seemingly ok with FAT but experience failures with ext2 (FAT FS corruption can go by unnoticed by the OS for quite some time).

Note that CF cards don't seem to suffer the same compatibility issues (probably because the parallel bus oriented CF interface is far easier to implement than the tight serial timing required by SD).

[chal]

I have a sandisk 512 sd, formatted ext 2 and have used it for a home on Cacko, and now on tKc 1.0 (with the Cacko kernel upgrade). I have also used it as a place to to install apps on OPIE, Hybrid and tKc. It has never given me any problems other than some apps (very few) loading slowly. I never had the infamous "sandisk problem."