[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.

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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