[DRBD-user] Re: DRBD doesn't seem to scale to fast underlying hardware with typical database load

Casey Allen Shobe cshobe at bepress.com
Tue Aug 12 19:23:08 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.


On Aug 9, 2008, at 12:17 PM, Lars Ellenberg wrote:
> familiarize yourself with the concept of the DRBD activity log.
> the config parameter would be "al-extents".

I have, but no matter whether I adjust it very high or very low, it  
seems to make no difference.

> verify that your disk subsystem has a non-volatile write cache  
> enabled.

Yep.  Array write cache enabled when battery present, disk write  
caches disabled.

> then add to DRBDs configuration no-disk-flushes and no-md-flushes.
>
> see if that helps.

Very much so!  I have to do some more testing before I'll have  
comparative numbers, but it's looking quite tolerable at the least.   
Will report back later with more info.

Cheers,
-- 
Casey Allen Shobe
Database Architect, The Berkeley Electronic Press
cshobe at bepress.com (email/jabber/aim/msn)
http://www.bepress.com | +1 (510) 665-1200 x163




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