[OmniOS-discuss] Strange ARC reads numbers

[Filip Marvan]

Hello,

 

I have storage server with OmniOS LTS and 64 GB RAM. This server was
installed one year ago. There are about 50 ZVOLs on that server and they are
shared through Comstar iSCSI to KVM servers, which are using these ZVOLs for
virtual servers.

 

After installation, I created a simple Munin script for monitoring ARC and
L2ARC, which is using arcstat.pl script from Mike Harsch
(http://blog.harschsystems.com/2010/09/08/arcstat-pl-updated-for-l2arc-stati
stics/). 

 

Last week, there was realy huge drop in ARC read statistics (you can see
that in attachment). On that graph you can see Total ARC accesses per
second. The only thing, that we done in that time, was deletion of about 5
unused ZVOLs with many snapshots and some clones. There was no change in
virtual servers load. 

 

Is there anyone who have any idea, why deleting some data (ZVOLs and
snapshots) have so dramatic efect on ARC accesses? There was more that 60%
of free space on that ZFS pool.

 

Thank you!

Filip Marvan

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