[libvirt] [libvirt-users] Host OS, Storage Info

[Martin Kletzander]

On Thu, May 29, 2014 at 01:31:13PM -0400, Ainsworth, Thomas wrote:
>Martin, et al,
>
>Sorry for the lag in response.
>
>So I started playing with the various virsh commands.  Awesome.
>Been doing some reading and I believe I have some things configured not so
>well.
>As I stated earlier in the thread, we have all of the VM image files on one
>RAID5.  Very fast machine.
>
>When using top, the load average is a stable "5.xx".  No I/O wait. GB's of
>free memory.  Swap has not been touched.
>Using vmstat, I am writing to the RAID5 volume at a constant 150MB/s and
>reading at a constant 275MB/s.
>
>With all of that said, here are some results from virsh commands:
>
># virsh pool-list --all
>Name                 State      Autostart
>------------------------------------------------------
>default              active     yes
>
>
># virsh pool-info default
>Name:           default
>UUID:            xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
>State:          running
>Persistent:     yes
>Autostart:      yes
>Capacity:       30.76 GiB
>Allocation:     2.10 GiB
>Available:      28.66 GiB
>
>
>Now, is that ok to have all of the VM's using a default pool?
>Or should a pool be created for each VM instance.
>I honestly am not even sure what a pool references...?...
>

Pool is a set of volumes of the same type (iscsi, LVs, files in a
folder, etc.) in the same place.  Example is the default pool which is,
by default, in /var/lib/libvirt/images and volumes there are files
(pool type is "dir").  If you want to have all the domain disks in
that place and all the disks (volumes) should be files then default
pool is enough.

>The more I read, the more I am moving away from thinking something in the
>OS is the cause of my sluggishness.
>

I haven't read your previous mail before, so I've found that now.  How
often are you dropping those caches?  That won't help you not to use
swap.  Having memory occupied by buffers and caches is good if you
read/write from/to disks.  Even when the reads/writes are as fast as
you mentioned, reading/writing from/to RAM is way faster and until
there's some free memory, why not use that?

Martin
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