Mike Fedyk
2001-Sep-19 23:36 UTC
Fwd: Re: Define conflict between ext3 and raid patches against 2.2.19
----- Forwarded message from Neil Brown <neilb@cse.unsw.edu.au> ----- On Wednesday September 19, mfedyk@matchmail.com wrote:> On Tue, Sep 18, 2001 at 09:08:32PM +1000, Neil Brown wrote: > > On Sunday September 16, mfedyk@matchmail.com wrote: > > > Hi, > > > > > > I'm trying to setup a 2.2 kernel that I can use for comparison to the latest > > > 2.4 kernels I've been testing, but I came accross a little problem with the > > > patches I've been trying to combine. > > > > > > I've already applied: > > > ide.2.2.19.05042001.patch > > > linux-2.2.19.kdb.diff > > > linux-2.2.19.ext3.diff > > > > > > And now I'm trying to apply raid-2.2.19-A1, and I get one reject in > > > include/linux/fs.h. > > > > You should be aware that ext3 (and other journalling filesystems) do > > not work reliably over RAID1 or RAID5 in 2.2. Inparticular, you can > > get problems when the array is rebuilding/resyncing. > > > > But if you only plan to use ext3 with raid0 or linear, you should be > > fine. > > > > Can you point me to an archive that describes how to trigger this bug? > > Was it in linux-raid or ext3-users or ...? > > MikeI don't remember exactly where or when I read it - either linux-raid or linux-kernel. It was asserted by Stephen Tweedie. The problem is that ext3 is very careful about when it writes buffer to disk : it won't release a buffer until the relevant journal entry is committed. However when a RAID rebuild happens, every block on the array is read into the buffer cache (if it isn't already there) and then written back out again. This defeats the control that ext3 tries to maintain on the buffer cache. I don't know exactly what large-scale effects this might have. It could be simply that a crash at the wrong time could leave the filesystem corrupted. But I heard of one person who claimed to get filesystem corruption after using reiserfs over RAID1 in 2.2, so maybe it's worse than that. If you really need to know, I suggest you ask on ext3-users. NeilBrown ----- End forwarded message ----- Hello, As requested, I have forwarded this thread to ext3-users, and I'm asking the question again here. Were there any specific steps needed to reproduce the error, and with some testing help from me, would anyone be willing to try to fix this bug? Thanks, Mike
Bill Rugolsky Jr.
2001-Sep-19 23:44 UTC
Re: Fwd: Re: Define conflict between ext3 and raid patches against 2.2.19
On Wed, Sep 19, 2001 at 04:36:04PM -0700, Mike Fedyk wrote:> I don't know exactly what large-scale effects this might have. It > could be simply that a crash at the wrong time could leave the > filesystem corrupted. But I heard of one person who claimed to get > filesystem corruption after using reiserfs over RAID1 in 2.2, so maybe > it's worse than that.IIRC, if you disable the background rebuild, and do rebuilds manually on unmounted partitions, you will be OK with RAID1 (but not RAID5). Can anybody confirm? Regards, Bill Rugolsky