On 29 Jul 2003, Ron Johnson wrote: > On Tue, 2003-07-29 at 10:14, Vivek Khera wrote: > > >>>>> "GS" == Greg Stark <[EMAIL PROTECTED]> writes: > > > > GS> "scott.marlowe" <[EMAIL PROTECTED]> writes: > > > > GS> But you have to actually test your setup in practice to see if it > > GS> hurts. A big data warehousing system will be faster under RAID5 > > GS> than under RAID1+0 because of the extra disks in the > > GS> stripeset. The more disks in the stripeset the more bandwidth you > > GS> get. > > > > Anyone have ideas on 14 spindles? I just ordered a disk subsystem > > with 14 high speed (U320 15kRPM) SCSI disks to hook up with a dell > > PERC3/DC controller (only 128MB cache, though). > > 14 drives on one SCSI card, eh? I'd be worried about saturating > the bus.
I'm pretty sure those PERCs are based on the megaraid cards, which can handle 3 or 4 channels each... > Maybe it's an old rule of thumb, but I would fill a SCSI chain > more than half full. It's an old rule of thumb, but it still applies, it just takes more drives to saturate the channel. Figure ~ 30 to 50 MBytes a second per drive, on a U320 port it would take 10 drives to saturate it, and considering random accesses will be much slower than the max ~30 megs a second off the platter rate, it might take more than the max 14 drives to saturate U320. ---------------------------(end of broadcast)--------------------------- TIP 7: don't forget to increase your free space map settings