Hi! > Are you using virtio-block? Yes. > In any case, not using a released version always has risks. Well, what do you mean by "not using a released version"? The package "gentoo-sources" always uses released kernels. 2.6.30-r2 in Gentoo means that this is the third update of the stable kernel version 2.6.30. The "-r*" releases just contains small patches from the Gentoo kernel package maintainers. Thanks! Robert Amit Shah wrote: > On (Thu) Jul 09 2009 [08:27:48], Robert Wimmer wrote: > >> Hi there, >> >> back in days before kernel 2.6.25/2.6.26 and KVM 70-77 KVM decided to >> crash from time to time. That time we used XFS as filesystem (/ and /boot >> where ext3/ext2). Since XFS worked so very well for us on physical >> hosts the natural choise for our OSs in KVM of course was also XFS. >> This was a bad idea because it caused some filesystem corruptions >> on some KVMs when KVM crashed (without any message). >> Somewhere I read that XFS in KVM should only be used with the >> KVM parameter "cache=none". Since then this is now our default >> for all KVMs (even with ext3). I thought by myself that KVM and an FS which >> does heavy write caching like XFS is a bad choise so I decided that I can't >> trust XFS inside a KVM anymore and so I switched all filesystems >> in our KVMs to ext3. This was a good choice. No FS corruptions >> anymore - well and no unplaned crashes of of KVM too ;-) >> Since yesterday (no crash but FS corruptions)... >> >> I installed kernel 2.6.30-r2 in one of our guests. This was a not so >> good idea. All hosts and guest running Gentoo. Host kernel is 2.6.29-r5 >> and KVM is 84 (KVM 85 has issues with VNC display and 86 and >> 87 not in portage currently). Using qow2 as KVM image format. >> >> I installed all the stuff we needed in the new KVM and a Postgres >> database. But something was different. The database import was >> suddenly fast as hell. I've never seen such good I/O throughput >> in a KVM. Well after almost finished with the whole installation >> process I noticed some strange ext3 messages in the "dmesg" >> output. "Oh no... Not again problems with FS corruptions" I thought... >> Well after a reboot of the KVM it was sure that the rootfs was >> corrupted. /etc/hostname and some other files suddenly were >> binary files :-( Lukely I was able to correct the problems with >> fsck and get the files back from the backup. >> >> So what happend in 2.6.30? Ah... I remembered immediately that >> the kernel developers decided to switch the default value of the >> journaling mode (data=...) from "ordered" to "writeback". Well... >> Now I know why the database import was so fast... But at what >> price? I'm really curious what happens when the major distributions >> roll out their distributions with this default option. >> > > Distributions will likely change the default. > > >> So my question is: I'm the only one in the universe with this >> FS problems? Am I completely wrong here? Is "data=ordered" >> the recommended mode for ext3 in KVMs and even necessary >> when KVM ist not crashing? This kind of stuff sometimes makes >> live to so easy... ;-) >> > > Are you using virtio-block? > > In any case, not using a released version always has risks. > > Amit > -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
