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? :) Sam Sam