EXT4-fs (sda6): Unaligned AIO/DIO on inode N by VirtualBox; performance will be poor

[euroford]

The same problem, https://bugzilla.kernel.org/show_bug.cgi?id=36722
bug in ext4 filesystem, not solved yet.

[MiG82au]

euroford, did actually you read the bug report? It's unrelated.

[masuch]

I have came across this error as well:
EXT4-fs (sdcX): Unaligned AIO/DIO on inode NNN by VirtualBox; performance will be poor.
But I did not notice any performance degradation.

[fbcyborg]

Hi!

I had the same problem after moving my VDI directory to an external USB 3.0 hard drive with ext4 fs.
Actually, I've noticed low speed with my virtual machines. Do you think it would be better to use XFS instead?

[mariposil]

bad news:

http://askubuntu.com/questions/118140/unaligned-aio-dio

[imbjr]

bad news:

http://askubuntu.com/questions/118140/unaligned-aio-dio

I'm still getting this in my logs and I've never seen any real issue with it. Glad to know it's not something more critical.

[SteveONCSU]

I'm seeing this same problem. So how do you realign the VDI hard disk? I don't notice any performance problem but I would like to get rid of this message.

[drbin]

have the same on raid-1 sata disks Dell server.
could it be the host i/o option under the drives selection tab?
I usually prefer to uncheck.

[karlmikaze]

For what it's worth, here's my further findings on this topic.

I stumbled upon an IBM devworks article dated 04/2010 that includes some benchmarks and impact scenarios using different filesystems:
http://www.ibm.com/developerworks/li...-sector-disks/

The essence, as I understood it:

• if you're seeing this error on Advanced Format type drives (newer, bigger HDs, using default 4k blocksize), the speed penalty is substantial. You should rethink your partitioning layout and probably move away from 512k block size in linux.
• If you're (like me) on a HW RAID5 of bigger, newer disks and seeing this error, the penalty for ext4 filesystems on top is somewhere between 5-30%.
• YMMV with other filesystems etc.

In my use case (SATA disks in HWRAID5, lvm2 on top, ext4 fs), I decided to live with the daily warning and the (neglecable) performance hit - which I didn't notice yet in real life.

hth Chris

[CharlesA]

I'm seeing this same problem. So how do you realign the VDI hard disk? I don't notice any performance problem but I would like to get rid of this message.

I have the same thing, but only with only 1 of my VDIs. I will see if exporting it and importing it fixes it.

EDIT: It turned out the problem was that VM didn't have "Use host I/O cache" enabled. All good now.