[PVE-User] PBS : is dirty-bitmap really accurate ?
daniel at firewall-services.com
Thu Jul 23 08:53:01 CEST 2020
----- Le 23 Juil 20, à 8:43, Fabian Grünbichler f.gruenbichler at proxmox.com a écrit :
> possibly you haven't upgraded to pve-qemu-kvm 5.0-11 (or your VM hasn't
> been restarted yet since the upgrade):
I'm running pve-qemu-kvm 5.0.0-11, and all the implied VM have been either (cold) rebooted, or migrated.
> the bitmap has a granularity of 4MB, so depending on the activity inside
> you can see quite a bit of amplification. also writing and then
> zeroing/reverting again to the old content would leave a mark in the
> bitmap without permanently changing the contents.
Yes, I'd expect some amplification, but not that much. For my Zabbix server, it's nearly canceling all the benefit of using a dirty bitmap.
One thing I've noted, is that I get expected values at least for one guest, running PfSense (where I get ~150MB of dirty blocks each days). Most of my other VM are Linux, I'll check if it could be related to the atime update or something
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