[Gluster-devel] IO errors when booting VM images on gluster volume via FUSE mount

[Anand Avati]

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 <lancelotds at 163.com> 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" <anand.avati at gmail.com> 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 <lancelotds at 163.com> 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" <bharata.rao at gmail.com> 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/
>>
>>
>> >
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>> >Gluster-devel at nongnu.org
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>>
>>
>>
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>
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