Perhaps someone will clue me in to what IIRC actually means. My first thought was that you are comparing new IDE drive technology to 4 year old SCSI technology. SOA of SCSI is ultra3 (160mbs) and ultra controller like the Adaptec 29160 and 10,000 - 15,000 WD ultra3 drive would probably dust the IDE's but you surely caught my attention with your post. Then there are hardware RAID controllers that should really optimize performance. Also I don't seem to get the same reliability from IDE on servers that I get from SCSI - however most of my firsthand comes from Windows NT which seems to pretty well thrash an IDE drive in a years time. Craig > -----Original Message----- > From: plug-discuss-admin@lists.plug.phoenix.az.us > [mailto:plug-discuss-admin@lists.plug.phoenix.az.us]On Behalf Of > sinck@ugive.com > Sent: Wednesday, October 18, 2000 9:11 AM > To: plug-discuss@lists.plug.phoenix.az.us > Subject: IDE vs SCSI drives > > > > \_ [root@saguaro kev]# /sbin/hdparm -tT /dev/sda /dev/hde /dev/md0 > \_ > \_ /dev/sda: > \_ Timing buffer-cache reads: 128 MB in 1.02 seconds =125.49 MB/sec > \_ Timing buffered disk reads: 64 MB in 5.05 seconds = 12.67 MB/sec > \_ > \_ /dev/hde: > \_ Timing buffer-cache reads: 128 MB in 1.03 seconds =124.27 MB/sec > \_ Timing buffered disk reads: 64 MB in 2.64 seconds = 24.24 MB/sec > \_ > \_ /dev/md0: > \_ Timing buffer-cache reads: 128 MB in 0.90 seconds =142.22 MB/sec > \_ Timing buffered disk reads: 64 MB in 2.69 seconds = 23.79 MB/sec > \_ > \_ (I've run this test a number of times and there's not much variation > \_ in the results.) > \_ > \_ According to the hdparm manpage, the buffer-cache read numbers are > \_ "essentially an indication of the throughput of the processor, cache, > \_ and memory of the system under test." I don't know why the number was > \_ so much higher for the md device. (This is the RAID-1 device which > \_ represents the mirrored /dev/hde5 and /dev/hdg5 partitions.) > > IIRC, the RAID howto mentions that READs can be faster on a RAID1 > because it just has to wait for the first disk to respond. So, > depending on magic hardware differences, you'll get slightly better > performance from that. > > \_ The SCSI disk averaged 7.592 seconds to do the copy. The IDE disk(s) > \_ averaged 4.3820 seconds. Remember that for the latter operation, the > \_ OS has to write to *both* disks which form the mirror. This comes out > \_ to 8.43 MB/sec for my SCSI disk and 14.61 MB/sec for the IDE disk > \_ array. (I should try to find a way to write to just one disk to see > \_ how much performance the RAID-1 is costing me.) > > De RAID one of the partitions... > > \_ SCSI subsystem driver Revision: 1.00 > \_ (scsi0) found at > PCI 0/14/0 > \_ (scsi0) Wide Channel, SCSI ID=7, 32/255 SCBs > \_ (scsi0) Downloading sequencer code... 392 instructions downloaded > \_ scsi0 : Adaptec AHA274x/284x/294x (EISA/VLB/PCI-Fast SCSI) 5.2.1/5.2.0 > \_ > \_ Vendor: HP Model: C6270A Rev: 3846 > \_ Type: Processor ANSI SCSI revision: 02 > \_ (scsi0:0:6:0) Synchronous at 80.0 Mbyte/sec, offset 31. > \_ Vendor: QUANTUM Model: QM318000TD-SW Rev: N491 > \_ Type: Direct-Access ANSI SCSI revision: 02 > \_ > \_ Note the 80.0 Mbyte/sec line. > > Perhaps the synchronous part? It's been a while, but isn't there an > async mode? Would that be wise? > > \_ Comments? In particular, I'd like those SCSI advocates to speak up > \_ and let me know what I'm doing wrong with my SCSI drive. (I'd hate to > \_ think that I've been paying more money all of these years for less > \_ performance.) > > Could it be that your SCSI drive itself isn't pumping at full rate? > Like a 5400 RPM drive is prolly going to be slower than a 7200 or 10k > drive...? > > I also think part of the advantage of SCSI is multiple devices on the > same controller, not a 1-1 pairing. > > David > > ________________________________________________ > See http://PLUG.phoenix.az.us/navigator-mail.shtml if your mail > doesn't post to the list quickly and you use Netscape to write mail. > > Plug-discuss mailing list - Plug-discuss@lists.PLUG.phoenix.az.us > http://lists.PLUG.phoenix.az.us/mailman/listinfo/plug-discuss