[PVE-User] PBS : is dirty-bitmap really accurate ?
daniel at firewall-services.com
Wed Jul 22 18:40:34 CEST 2020
I've started playing with PBS on some VM. So far, it's looking really promizing.
There's one strange thing though : the percent of the dirty data. For example, I backup one VM every 2 or 3 days. It's a moderately busy server, mainly serving a MariaDB database (zabbix server + mariadb). On each backup, I get similar dirty values :
INFO: using fast incremental mode (dirty-bitmap), 492.7 GiB dirty of 590.0 GiB total
While I'm sur not even 10% of this has really been written.
Get more or less the same problem on other VM. One which I know just sleep all day (my personnal OnlyOffice document server), and which I backup daily, and get values like :
INFO: using fast incremental mode (dirty-bitmap), 5.0 GiB dirty of 10.0 GiB total
Or another small one (personnal samba DC controler) :
INFO: using fast incremental mode (dirty-bitmap), 13.0 GiB dirty of 20.0 GiB total
The only write activity for those 2 are just a few KB or maybe MB of log lines. Respectivly 5 and 13GB of dirty blocks seems unreal.
Am I the only one seeing this ? Could the dirty-bitmap mark dirty blocks without write activity somehow ?
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