Posts Tagged ‘filesystem’

Xen Virtual Disk I/O Errors

I just encountered this while making a tar backup on one of my virtual filesystems:

lost page write due to I/O error on xvdb1
end_request: I/O error, dev xvdb1, sector 33707688
Buffer I/O error on device xvdb1, logical block 4213461

Unfortunately, my fs suffered corruption.

Some folks, particularly Ubuntu users with kernel 3.2.x seem to say the answer is adding

barrier=0

to your ext3/ext4 mount options.

In my case I’m pretty sure an OOM error killed something critical to the backend on dom0.

Be sure to check your dom0′s dmesg.

UPDATE Uhh yeah, something actually managed to overflow the dom0′s fs. >.> This is what I was getting in the dom0 dmesg:

loop: Write error at byte offset 17820364800, length 4096.

for which there is very little discussion, but a quick df told me what was going on.

Force File System Check (fsck) on Reboot

You may wish to check the integrity of your root file system without using a live cd or different system. To force a file system check on reboot either:

# touch /forcefsck

or

# shutdown -rF now

Move Zimbra Storage to Different Drive/File-System

If your Zimbra server’s storage is running out or you try to keep your virtual machines lean and easily transferrable it might be necessary to put Zimbra’s mail storage on a different file system or storage medium.

The process is straightforward; they key is knowing that Zimbra stores mail in /opt/zimbra/store.

In my case, I’m creating and attaching a 20 GB sparse file to a virtual machine:

# dd if=/dev/zero of=storage.img seek=20000 bs=1M count=0
# mke2fs -j storage.img

After attaching your storage and creating the file system boot your Zimbra server (if necessary) and mount the file system to /mnt/tmp

# mkdir /mnt/tmp
# mount /dev/sda2 /mnt/tmp

Shut down Zimbra if it is running.

# /etc/inid.d/zimbra stop

Change the ownership of the new file system’s root directory to your zimbra user:

# chown zimbra: /mnt/tmp

Move the contents of /opt/zimbra/store (or wherever your store directory is located) to /mnt/tmp:

# mv /opt/zimbra/store/* /mnt/tmp/

Unmount /mnt/tmp:

# umount /mnt/tmp

Now create an appropriate fstab entry for /opt/zimbra/store using the new file system’s device node/label/etc.:

/dev/sdb1       /opt/zimbra/store       ext3    defaults,noatime        0 0

Mount /opt/zimbra/store and start Zimbra:

# mount /opt/zimbra/store
# /etc/init.d/zimbra start
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