We've identified I/O latency on SQL Server portion of our farm. We see tempdb and CrawlDB are biggest offenders. We have 2 extra Raid 1 disks available to us. Let's call them X: and Z:. The question is, will we see more bang for the buck by doing which of the following:
Option 1: X: tempdb.mdf Z: tempdb.ldf
Option 2: X: tempdb .mdf + .ldf Z: CrawlDB .mdf + .ldf
I know general best practices dictate that you separate .ldf and .mdf, but wondering if we can expect to see a bigger bang for the buck if we move crawldb off to separate hardware too. I know we'll need to monitor/test/etc to be sure...
The guidance from MS is a little fuzzy on this (my emphasis added):
Testing and customer data show that SharePoint Server 2010 farm performance can be significantly impeded by insufficient disk I/O for tempdb. To avoid this issue, allocate dedicated disks for tempdb. If a high workload is projected or monitored — that is, the average read operation or the average write operation requires more than 20 ms — you might have to ease the bottleneck by either separating the files across disks or by replacing the disks with faster disks.