On Saturday 14 May 2005 10:22, [EMAIL PROTECTED] wrote: > Hardware: SATA RAID adapter with SiliconImage 3114 chip. 2 SATA HDD. > I did gmirror.
<snip> > a) This is gmirror feature ? > b) This is hardware feature (SiliconImage 3114 chip) ? I don't think is related to your hardware. I have a Dell PowerEdge SC1425 which is exhibiting the same behaviour from gmirror, my disc controller is an onboard Intel ICH5. System: FreeBSD 5.4-STABLE @ Sun Apr 10 14:07:46 UTC 2005 atapci1: <Intel ICH5 SATA150 controller> port 0xccc0-0xcccf,0xccd8-0xccdb, 0xcce0-0xcce7,0xccf0-0xccf3,0xccf8-0xccff irq 18 at device 31.2 on pci0 ata2: channel #0 on atapci1 ata3: channel #1 on atapci1 mail# dmesg | grep ad4 ad4: 76293MB <ST380013AS/8.12> [155009/16/63] at ata2-master SATA150 mail# diskinfo -t ad4 <snip> Seek times: Full stroke: 250 iter in 5.606627 sec = 22.427 msec Half stroke: 250 iter in 4.382610 sec = 17.530 msec Quarter stroke: 500 iter in 6.969860 sec = 13.940 msec Short forward: 400 iter in 1.940076 sec = 4.850 msec Short backward: 400 iter in 2.349238 sec = 5.873 msec Seq outer: 2048 iter in 0.228509 sec = 0.112 msec Seq inner: 2048 iter in 0.237599 sec = 0.116 msec Transfer rates: outside: 102400 kbytes in 1.755089 sec = 58345 kbytes/sec middle: 102400 kbytes in 2.106003 sec = 48623 kbytes/sec inside: 102400 kbytes in 3.496732 sec = 29284 kbytes/sec Pretty reasonable results. mail# dmesg | grep ad6 ad6: 76319MB <ST380817AS/3.42> [155061/16/63] at ata3-master SATA150 The second drive achieves slightly better seeking, but lower throughput. But the variation between ad4 and ad6 is very small as I would expect for two virtually identical drives. mail# diskinfo -t ad6 <snip> Seek times: Full stroke: 250 iter in 4.936300 sec = 19.745 msec Half stroke: 250 iter in 3.675749 sec = 14.703 msec Quarter stroke: 500 iter in 5.970199 sec = 11.940 msec Short forward: 400 iter in 1.937453 sec = 4.844 msec Short backward: 400 iter in 2.347955 sec = 5.870 msec Seq outer: 2048 iter in 0.211831 sec = 0.103 msec Seq inner: 2048 iter in 0.218748 sec = 0.107 msec Transfer rates: outside: 102400 kbytes in 1.754634 sec = 58360 kbytes/sec middle: 102400 kbytes in 2.107054 sec = 48599 kbytes/sec inside: 102400 kbytes in 3.522545 sec = 29070 kbytes/sec Now the same test against the gmirror: mail# diskinfo -t /dev/mirror/gmirror0 <snip> Seek times: Full stroke: 250 iter in 1.347611 sec = 5.390 msec Half stroke: 250 iter in 1.335664 sec = 5.343 msec Quarter stroke: 500 iter in 2.653382 sec = 5.307 msec Short forward: 400 iter in 2.254421 sec = 5.636 msec Short backward: 400 iter in 2.057330 sec = 5.143 msec Seq outer: 2048 iter in 0.265052 sec = 0.129 msec Seq inner: 2048 iter in 0.274519 sec = 0.134 msec Transfer rates: outside: 102400 kbytes in 2.774400 sec = 36909 kbytes/sec middle: 102400 kbytes in 3.138420 sec = 32628 kbytes/sec inside: 102400 kbytes in 4.498140 sec = 22765 kbytes/sec The seek times are way down, which is great, and makes sense using a round-robin strategy on the mirror, but my peak transfer rate has been almost halved too. I don't mind this too much as in my application low seek times are worth more than high transfer rates, but it is still puzzling to me to see such a remarkable drop in throughput. Thanks very much for insight, -- Dominic GoodforBusiness.co.uk I.T. Services for SMEs in the UK. _______________________________________________ freebsd-stable@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to "[EMAIL PROTECTED]"