[DRBD-user] Sudden high CPU load

Felix Frank ff at mpexnet.de
Wed May 18 09:20:43 CEST 2011

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


On 05/18/2011 04:09 AM, Richard Stockton wrote:
> Hi drbd folks,
> 
> We have been using DRBD with heartbeat for several years now.
> The load averages on our RedHat servers have almost always stayed
> below 1.0.  Suddenly last week the loads jumped up to 12-14 on
> both servers.  They go down at night, when the usage goes down,
> but by mid-day every business day they are back to 14.
> 
> We don't see anything out of the ordinary in logs, no drive
> warning lights, no degraded RAID, nothing especially out of
> bounds in iostat, NFS is running smoothly, tcpdump doesn't
> show any nastiness (that we can see)....
> We have run out of ideas.
> 
> Our setup is 2 disk arrays, with each server the fail-over for
> the other.  These are POP/IMAP accounts with half the alphabet
> on one server and half on the other.  If one server fails, the
> other one takes over all of the alphabet.  Each letter is a
> separate resource, with a separate IP, etc.  The size of the
> letter partitions range from 5G to 120G.  The pop/imap servers
> access the letters via NFS3.
> 
> RedHat 5.3 (2.6.18-128.1.10.el5)
> DRBD 8.3.1
> Heartbeat 2.1.4
> 
> Has anyone seen this sort of behavior before, and if so, what
> the heck is happening?  We would appreciate any suggestions.

Is NFS mounted sync or async?

Which I/O scheduler is in use for your DRBDs (i.e., for their backing
devices)?

Regards,
Felix



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