[DRBD-user] MySQL-over-DRBD Performance

Art Age Software artagesw at gmail.com
Sat Dec 15 20:32:51 CET 2007

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

> >> In my case, I am replacing a 3-year old pair of Dell 2850's (4GB,
> >> Dual-Proc/Single-Core)  with a pair of new  Dell 2950's (8GB,
> >> Dual-Proc/Quad-Core). Clearly, I expect to see an overall performance
> >> boost from the new servers. And for most operations I am seeing better
> >> performance. However for writes, I am seeing **worse** performance.
> >> **But only when the database is located on the DRBD device.**
> I've also set up a very similar cluster, and we have seen some performance
> degration due to DRBD but I haven't numerically measured it, and it hasn't
> impacted the cluster to the extent that we feel it warrants investigation.
> That being said, we know that write performance isn't what we want it to be
> but that has largely been attributed to running with 'sync_binlog' turned on
> in MySQL. We are planning to mitigate this with a battery backed RAID card
> so we can enable write-back caching without fear of data loss.
> In some tests we've performed with write queries we've seen quite signifant
> performance gains, in the hundreds of percent faster with the write-back
> caching.

Thanks for your reply. My storage subsystem on both nodes is a PERC
RAID-10 with battery-backed write-back cache enabled. The database is
all InnoDB and sync_binlog is enabled. I was under the impression that
sync_binlog should be enabled regardless of the presence of
battery-backed cache. Is this not the case?

It seems that there is a lot of uncertainty out there regarding how to
best configure MySQL on DRBD. Some sort of "best practices" document
with configuration settings for DRBD and MySQL would be a huge help in
this regard. I realize there are a lot of variables to take into
consideration. But having some solid tested examples to start from
would be quite helpful. Anyone up to the task?  :)



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