[DRBD-user] online verification really bogs things down

Florian Haas florian.haas at linbit.com
Sun Jul 20 08:39:51 CEST 2008

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.


Gregor Mosheh wrote:
> Online verification - very neat. Combined with the realtime write
> verification, this should completely eliminate the possibility of the
> data ever not being identical.
> 
> However, running an online verification is really intensive, as was
> warned in the manual. So intensive is it, that the rest of the system
> comes near to useless.

Let me guess... your syncer rate is way above what your storage
subsystem and/or network can handle?

> Does there exist a way to renice it or ionice it to reduce the load it
> causes, or to pause it? For example, what drbd.conf directives would be
> relevant to the verification speed as opposed to the sync speed?

No. The syncer rate also throttles online verification. So, the
considerations outlined in
http://www.drbd.org/users-guide/s-configure-syncer-rate.html also apply
to online verify. If you don't follow the rules of thumb outlined there,
both online verify and background sync are likely to bog down your system.

Cheers,
Florian

-- 
: Florian G. Haas
: LINBIT Information Technologies GmbH
: Vivenotgasse 48, A-1120 Vienna, Austria

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