[Fwd: Power Down]
Quoted 9 lines · David Woodhouse
Quoted 5 lines · [email protected] said:
The only way to be resistant to power failures in the file system level is to use a log-structured file system.
I heard ext3 is log-structured but I am sure one of the Linux guys here knows more about this,
ext3 is a journalling filesystem. I believe that it's not log-structured.
Is ext3 already available in beta form? Is it included in the latest 2.3.x kernels?
Quoted 3 lines
Journalling is sufficient for protection from power failures. Stephen, would you care to elaborate on the difference?
What is the overhead of Journalling? (CPU AND flash space). Of course if that solves the problem, then that is the most important thing (for me at least).
Quoted 11 lines
Quoted 3 lines
Any other file system that takes power failures into account, (I am afraid to guess NFTL ????).
I believe that NTFS is also journalling but not log-structured.
Quoted 1 line
Some of our customers use their own home brewed LFSs and do it successfully.
Personally, I'm inclined to believe that we should run a filesystem directly on the flash device - rather than faking a block device and running a 'normal' filesystem on top of that.
I think that would probably be the best idea also, since in repairing low level partitions vs a higher level f/s, could get really difficult to prove that it is reliable.
The only problem with this approach is that it is not the usual "linux" layered approach. But maybe that approach does not work well with embedded systems and is a hit we are willing to accept?
Another problem with the usual "layered" approach is that the VFS uses a lot of buffering in its layer. This is usually desirable for read/write performance, however for logs etc. on FLASH this is probably NOT desirable.
When I write a log, I want it written and saved. I guess one could do sync() etc. every time but not very elegant.
Quoted 4 lines
I've been rushed off my feet here with other things for a while, but as soon as I get back to it, after I've fixed the NFTL and DiskOnChip Millennium support, that's what I'm intending to look at.
Do you have an estimate for the time frame that you are looking at?
I am willing to help out with coding, as I am extremely interested in this (and
have access to lots of different embedded hardware with FLASH, SRAM etc. on it, and if needed I could possibly buy more :).
Quoted 8 lines
If you're running ext2 on a DiskOnChip you should mount it with the noatime option if you can - this will eliminate a lot of write activity.
--
dwmw2To unsubscribe, send "unsubscribe mtd" to [email protected]
To unsubscribe, send "unsubscribe mtd" to [email protected]
Quoted 5 lines · [email protected] said:
Quoted 3 lines
I've been rushed off my feet here with other things for a while, but as soon as I get back to it, after I've fixed the NFTL and DiskOnChip Millennium support, that's what I'm intending to look at.
Do you have an estimate for the time frame that you are looking at?
We have an EU research project coming to an end in February/March, and I'm running our end of it.
I'm hoping to snatch a few days in the next week or two to merge in all the MTD fixes I've been sent and look at the problems which have been reported, and make a new release.
After that, I'm unlikely to be able to be very productive until mid-to-late Feb.
Quoted 3 lines
I am willing to help out with coding, as I am extremely interested in this (and have access to lots of different embedded hardware with FLASH, SRAM etc. on it, and if needed I could possibly buy more :).
I have documentation on NFTL and the DiskOnChip hardware which I am permitted to release under NDA to someone who is serious about contributing to the development - your assistance would be greatly appreciated because I was hoping to have that completed by now.
There is also some work to be done with FTL on NOR flash, I believe. It should work, but apparently there are some problems with it. I don't currently have access to any NOR flash devices so haven't tested it recently.
Also, someone needs to provide new PCMCIA bulkmem drivers which use the MTD system.
There's plenty of work to go round.
--
dwmw2
To unsubscribe, send "unsubscribe mtd" to [email protected]