From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bill Davidsen Subject: Re: no journaling and loops on softraid? Date: Wed, 07 Mar 2007 11:49:09 -0500 Message-ID: <45EEED05.5030600@tmr.com> References: <200703052355.15363.Dexter.Filmore@gmx.de> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <200703052355.15363.Dexter.Filmore@gmx.de> Sender: linux-raid-owner@vger.kernel.org To: Dexter Filmore Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids Dexter Filmore wrote: > http://gentoo-wiki.com/HOWTO_Gentoo_Install_on_Software_RAID#Data_Scrubbing > > "Warning: Be aware that the combination of RAID5 and loop-devices will most > likely cause severe filesystem damage, especially when using ext3 and > ReiserFS. Some users suggest that XFS is not affected by this, but this has > not been entirely confirmed. See kernel bug 6242 for updates on this bug. > > Note: There are also reports that Journaled Filesystems are problematic on all > Software-RAID levels. No kernel bugs have been submitted regarding this bug > as of yet. A number of the reports involve using cryptoloops which are known > to cause corruption. See http://forums.gentoo.org/viewtopic-t-412467.html for > more information. This thread should be taken with a grain of salt." > > Can someone shed some light on this? I have XFS on my raid and *had* problems > when unpacking large archives with many small files. > To start, the report mentions a number of unrelated layers, evms, dm-crypt, and some total misinformation, claiming that evms is needed to allow growing of raid. I can't speak to XFS over RAID, I've seen report of XFS problems on native partitions, and just don't have enough information to have a good opinion. But I have been running ext3 over RAID1 and RAID5 for years, and just haven't seen the problems you mention, or anything else which concerns me. There were recovery issues in early kernels, but I have no reason to think that there's any basic problem at this point. Reports of problems often outlive the problem, and problems with multiple layers of device manipulation you increase the chance of failure, because a chain is as strong as the weakest link, and decrease the chances if identifying which layer is actually a problem. If you have any hardware issues, you now depend on every layer not only handling them, but passing them up and down layers. I have put lvm over raid, but even that would be an issue to debug. I would simplify if I had your problem. -- bill davidsen CTO TMR Associates, Inc Doing interesting things with small computers since 1979