That is probably because with cache=writeback write-behind is exercised which can give a huge boost in performance. I am suspecting that a recent commit in write-behind might have broken something. Using write-behind should be safe for normal operation.
On Tue, Aug 7, 2012 at 2:31 AM, Jules Wang <[email protected]> wrote: > hi, Anand: > Another question on "writeback" is: I observe disk performance > boost(40x)(using IOMeter in VM) when setting cache=writeback in comparsion > with cache=none or writethrough. > Do you have any ideas about that? :-) > > Best Regards. > > Jules Wang > > > > At 2012-08-07 15:10:30,"Anand Avati" <[email protected]> wrote: > > cache=writeback should not be necessary (including disabling > write-behind). This is clearly a bug. We are looking into it. > > On Mon, Aug 6, 2012 at 11:51 PM, Jules Wang <[email protected]> wrote: > >> Bharata: >> Alternatively,You could add ",cache=writeback" after "if=virtio". >> Good Luck. >> >> Best Regards. >> Jules Wang >> >> >> At 2012-08-07 14:29:38,"Bharata B Rao" <[email protected]> wrote: >> >Hi, >> > >> >With latest QEMU and latest gluster git, I observe guest root >> >filesystem corruption when the VM boots. >> > >> >QEMU command line I am using is this: >> >qemu-system-x86_64 --enable-kvm --nographic -m 1024 -smp 4 -drive >> >file=/mnt/F17,if=virtio -net nic,model=virtio -net user -redir >> >tcp:2000::22 >> > >> >Gluster volume is mounted in this manner: >> >glusterfs -s bharata --volfile-id=test -L DEBUG -l glusterfs.log /mnt >> > >> >I see IO errors like this when VM boots: >> >[ 1.698583] end_request: I/O error, dev vda, sector 9680896 >> >[ 1.699328] Buffer I/O error on device vda3, logical block 1081344 >> >[ 1.699328] lost page write due to I/O error on vda3 >> >[ 1.706644] end_request: I/O error, dev vda, sector 1030144 >> >[ 1.707630] Buffer I/O error on device vda3, logical block 0 >> >[ 1.707630] lost page write due to I/O error on vda3 >> >[ 1.718671] dracut: >> >/dev/disk/by-uuid/d29b972f-3568-4db6-bf96-d2702ec83ab6: clean, >> >21999/623392 files, 796916/2492672 blocks >> >[ 1.723455] dracut: Remounting >> >/dev/disk/by-uuid/d29b972f-3568-4db6-bf96-d2702ec83ab6 with -o ro >> > >> >VM eventually comes up with RO rootfs. Shutdown path sees these kinds of >> >error: >> > >> >[ 16.034271] EXT4-fs (vda3): previous I/O error to superblock detected >> >[ 16.041699] end_request: I/O error, dev vda, sector 1030144 >> >[ 16.042679] EXT4-fs error (device vda3): ext4_remount:4418: Abort >> >forced by user >> >[ 16.046465] EXT4-fs (vda3): re-mounted. Opts: (null) >> > >> >Full glusterfs log is too big to go with this mail. I can see this >> >kind of errors: >> > >> >[2012-08-07 05:56:29.598636] T [io-cache.c:128:ioc_inode_flush] >> >0-test-io-cache: locked inode(0xd2d2c0) >> >[2012-08-07 05:56:29.598642] T [io-cache.c:132:ioc_inode_flush] >> >0-test-io-cache: unlocked inode(0xd2d2c0) >> >[2012-08-07 05:56:29.598651] T [fuse-bridge.c:2113:fuse_writev_cbk] >> >0-glusterfs-fuse: 319: WRITE => 4096/4096,4956618752/10737418240 >> >[2012-08-07 05:56:29.598749] T [fuse-bridge.c:2293:fuse_fsync_resume] >> >0-glusterfs-fuse: 320: FSYNC 0xd6f060 >> >[2012-08-07 05:56:29.598845] W [write-behind.c:2809:wb_fsync] >> >0-test-write-behind: write behind wb_inode pointer is not stored in >> >context of inode(0x7f9cb1eab0c0), returning EBADFD >> >[2012-08-07 05:56:29.598858] W [fuse-bridge.c:1063:fuse_err_cbk] >> >0-glusterfs-fuse: 320: FSYNC() ERR => -1 (File descriptor in bad >> >state) >> >[2012-08-07 05:56:29.605831] T [fuse-bridge.c:2154:fuse_write_resume] >> >0-glusterfs-fuse: 322: WRITE (0xd6f060, size=4096, offset=527433728) >> > >> >Just to clarify, I am not using GlusterFS block backend in QEMU (via >> >libgfapi) here but instead using it with normal FUSE mount. >> > >> >Regards, >> >Bharata. >> >-- >> >http://bharata.sulekha.com/blog/posts.htm, http://raobharata.wordpress.com/ >> >> >> > >> >_______________________________________________ >> >Gluster-devel mailing list >> >[email protected] >> >https://lists.nongnu.org/mailman/listinfo/gluster-devel >> >> >> >> >> _______________________________________________ >> Gluster-devel mailing list >> [email protected] >> https://lists.nongnu.org/mailman/listinfo/gluster-devel >> >> > > >
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