The Random Ramblings of a Sysadmin

Every few years I come across one of the little boxen, and every time I face the same issue. I can clearly remember that the RAID is slow for a reason, just not which reason. This posting is intended to save me from spending time on google in a few years... The Dell PowerEdge SC440 is a nice little Xeon-based tower server featuring a SAS 5/iR RAID controller. The sluggish writes are due to the default disabling of write cache on the controller, which is just fine for making sure data are not lost if the power fails, but which also drags performance down to ridiculous levels. It's not possible to enable write cache from the controller firmware menu. Here's how to work around that issue: If running FreeBSD, add 'hw.mpt.enable_sata_wc=1' to your boot.conf. If running Linux, use lsiutil to adjust the value directly in the RAID controller firmware. If running Windows, well, who does that sort of thing if performance matters? A few numbers from a quick write test under FreeBSD 7.2, using ZFS on top of the array: Write cache disabled, 32K chunks: 2 MB/s Write cache enabled, 32K chunks: 40 MB/s Please don't enable write cache and blame me for subsequent loss of data, limbs or partners.