On Tue, 13 Apr 2004, Christopher Petrilli wrote: > 2. Retrieval time is limited not by disk bandwidth, but by I/O seek > performance. More spindles = more concurrent I/O in flight. Also, this > is where SCSI takes a massive lead with tag-command-queuing. > > In our case, we ended up using a three-tier directory structure, so > that we could manage the number of files per directory, and then > because load was relatively even across the top 20 "directories", we > split them onto 5 spindle-pairs (i.e. RAID-1). This is a place where > RAID-5 is your enemy. RAID-1, when implemented with read-balancing, is > a substantial performance increase. Please explain why RAID 5 is so bad here. I would think that on a not very heavily updated fs, RAID-5 would be the functional equivalent of a RAID 0 array with one fewer disks, wouldn't it? Or is RAID 0 also a bad idea (other than the unreliability of it) because it only puts the data on one spindle, unlike RAID-1 which puts it on many. In that case >2 drive RAID 1 setups might be a huge win. The linux kernel certainly supports them, and I think some RAID cards do too. Just wondering. ---------------------------(end of broadcast)--------------------------- TIP 7: don't forget to increase your free space map settings
