Re: [ovirt-devel] Reporting vm disk stats "truesize" and "apparentsize"?
On 15 Sep 2016, at 18:18, Nir Soffer <nsoffer(a)redhat.com>
wrote:
Hi all,
Vdsm reports apparentsize and truesize disk stats [1] when getting
vms stats (every 15 seconds?). These values are update every
60 seconds in vdsm.
To collect the values, we run risky storage apis in vdsm virt thread
pool, and we want to avoid this [2] since one slow or broken domain
can cause the entire virt thread pool to get stuck and cause vms
using other (healthy) storage domain to become non responsive.
These can also break block storage thin provisioned disks, since they
depend also on the virt thread pool. So one bad NFS storage domain
can cause vms using only block storage to be paused.
If both of these values are not used by anyone, we would like to
stop reporting them.
there are only 2 consumers of the monitoring, engine and mom.
git grep reveals that “apparentsize" is used only for importing HE.
“truesize" too, but additionally it is used in engine storage code as an actual size
of the disk
If the values are used, we need to find a safer way to report them,
probably in storage thread pool, or maybe we can get these values
from libvirt using bulk sampling.
you could have been able to drop apparentsize right away, but the HE import code is
expecting that field and won’t be happy if it is missing
The monitoring code would work but fill in 0 for the actual size
Please update if these values are used in engine/dwh.
[1] https://github.com/oVirt/vdsm/blob/master/lib/vdsm/virt/vmstats.py#L364
[2] https://gerrit.ovirt.org/59801
Nir
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