On Saturday 14 May 2005 10:22, vohand@gmail.com 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.