Am Freitag, 11. Mai 2007 schrieb Feizhou: > > SATA and SCSI/SAS should give comparable single work-load sequential > > numbers, but most SCSI/SAS have better seek times so random IO will > > be better on those. Also SCSI/SAS support tagged command queuing, > > which allows multiple overlapping IOs so you will tend to see better > > mixed workload performance compared to SATA (multi-user environment). > > > > Having said that some of the new SATA models that support NCQ, the > > SATA version of TCQ, and that use some of the same SCSI/SAS onboard > > processing (Western Digital Raptors) can approach or equal SCSI/SAS > > mixed load performance, but their price also approaches or equals > > SCSI/SAS and their spindle speeds still do not top 10K so random > > will not be as good. > > Nope. SATA drives with NCQ support are in the same price range as non > NCQ drives, if not the same price, which is by far less costly than > SCSI/SAS drives. Also, due to the incredible packing to get 200GB-750GB > of space onto the platter, the lower RPM is made up for especially at > the higher densities. > > A 73GB 15K RPM SCSI/SAS drive is in the same price range as a 750GB 7.5K > RPM NCQ capable SATA drive. Ten times the density at half the speed. I > reckon it would give the SCSI drive a run for its money in regard to > random access times. > > The SCSI drive: > Spindle Speed 15000 rpm > Average latency 2.0 msec > Random read seek time 3.50 msec > Random write seek time 4.0 msec > > The SATA drive: > Spindle Speed 7200 rpm > Native Command Queuing Y > Average latency 4.16 msec > Random read seek time <8.5 msec > Random write seek time <10.0 msec > Maximum interface transfer rate 300 Mbytes/sec > > Without NCQ enabled, it will take twice as long as the scsi drive. With > NCQ enabled, the game changes. > > Compare to a 10K scsi drive: > Spindle Speed 10,000 rpm > Sustained data transfer rate 80 Mbytes/sec. > Average latency 3.0 msec > Random read seek time 4.9 msec > Random write seek time 5.4 msec > Maximum interface transfer rate 320 Mbytes/sec > > NCQ SATA is almost a no-brainer. Sorry, but you are comparing apples and oranges. Sure the SATA drives look good on paper, and sure they perform well in applications without lot's of parrallel IO/s and seeks around the whole disk. For a more useful comparison regarding fileservers or databaseservers look into the performance database of storagereview.com: http://www.storagereview.com/comparison.html Select for example "IOMeter File Server - 16 I/O". The top drives are all 15k SCSI or SAS, followed by 10K SCSI or SAS, followed by the raptors and than the rest of the SATA drives. Sure the SATA drives are still acceptable for a wide range of server applications, especially since you can use lots and lots because of their attractive price point. But still... apples and oranges. regards, Andreas Micklei -- Andreas Micklei IVISTAR Kommunikationssysteme AG Ehrenbergstr. 19 / 10245 Berlin, Germany http://www.ivistar.de Handelsregister: Berlin Charlottenburg HRB 75173 Umsatzsteuer-ID: DE207795030 Vorstand: Dr.-Ing. Dirk Elias Aufsichtsratsvorsitz: Dipl.-Betriebsw. Frank Bindel