[CentOS-virt] Confused by "qemu-img convert"
wkern at pixelgate.net
Sun Apr 24 01:49:53 EDT 2011
VBox 4.x is slower than 3.2.12. I can not take any
> more performance hits. I am still on 3.2.12 for the
> same reason you are using old-out-of-date Enterprise Linux.
> 8478 corrupted the hell out of a Visual Fox Pro and
> and M$SQL 2008 database.
hmm. interesting experience you had. Sorry you had to deal with that.
We've seen some disk issues on VB on EXT4 Ubuntu Guests. None of those
resulted in lost data because the filesystem went read-only when it had
an issue, but that rendered the image unusable, until resolved. We were
NOT running host I/O caching and turning that back on seems to have
solved the problem (though thats an entirely different issue since thats
a lot of data to be sitting around waiting for a write). Ext4 issues
identical to what we experienced were widely reported on the Ubuntu
lists on non-VM machines as well so we aren't yet prepared to blame VB.
We are still investigating performance. In most test cases, such as some
LAMP stack projects VB seems quite speedy and "feels" on par with other
VM solutions, though we haven't directly measured yet.
OTOH, we recently ran into an application where the MySQL performance
was orders of magnitude slower than the prior VM solution where it
resided. The app involved repeated executions of a very complex SQL
query and the speed hit was there irregardless of the RAM and number of
CPU's presented to the VB image, we traced and saw some sort of lock
contention and assume disk i/o was part of the problem.
We've been impressed with VB's teleportation, the ability to use RDP to
see whats going on, and the Xwin interface, which is more cross platform
(for us) than the VMware solution. We are disappointed in the lack of
readily available enterprise deployment tools.
Thanks for your feedback.
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