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SubjectRe: md RAID over SATA performance

On 2004.09.03, J.A. Magallon wrote:
> Hi all...
>
> I am buildin an array with a linux box, and I run 2.6.8.1 (not stock, but
> the mandrake cooker version).
>
> Disks are 6 SATA drives, plugged to a couple of Promise FastTrak S150 TX4
> cards.
>
> Problem is that i get really poor performance. A single drive gives about
> 57 Mb/s, and a raid1 with two just gives about 64 Mb/s (measured with
> hdparm -tT). With the six drives:
>
>

Thanks to everybody for its answers...

My confusion/problem was that I has always tried with only two drives,
and with more or less old drives that gave around 20-25Mb/s each, so
the raid worked very optimally at about 50 Mb/s.
But with modern drives at 55 Mb/s, I hit the PCI speed limits, I suppose.
Board is a Supermicro P3TDDE, Via ApolloPro 266T chipset (aghhh),
33 MHz PCI, 2xPIII@933.

With a stock 2.6.8.1, I get this:

nada:~# hdparm -tT /dev/md0

/dev/md0:
Timing buffer-cache reads: 864 MB in 2.00 seconds = 431.63 MB/sec
Timing buffered disk reads: 252 MB in 3.01 seconds = 83.85 MB/sec

with this setup:

nada:~# mdadm --detail /dev/md0
/dev/md0:
Version : 00.90.01
Creation Time : Fri Sep 3 02:17:28 2004
Raid Level : raid5
Array Size : 1225557760 (1168.78 GiB 1254.97 GB)
Device Size : 245111552 (233.76 GiB 250.99 GB)
Raid Devices : 6
Total Devices : 6
Preferred Minor : 0
Persistence : Superblock is persistent

Update Time : Fri Sep 3 19:01:39 2004
State : clean
Active Devices : 6
Working Devices : 6
Failed Devices : 0
Spare Devices : 0

Layout : left-symmetric
Chunk Size : 256K

UUID : fd6fcad0:21da140b:072a82b1:11b3db21
Events : 0.239

Number Major Minor RaidDevice State
0 8 1 0 active sync /dev/sda1
1 8 17 1 active sync /dev/sdb1
2 8 33 2 active sync /dev/sdc1
3 8 49 3 active sync /dev/sdd1
4 8 65 4 active sync /dev/sde1
5 8 81 5 active sync /dev/sdf1


--
J.A. Magallon <jamagallon()able!es> \ Software is like sex:
werewolf!able!es \ It's better when it's free
Mandrakelinux release 10.1 (RC 1) for i586
Linux 2.6.8.1-mm4 (gcc 3.4.1 (Mandrakelinux (Alpha 3.4.1-3mdk)) #8


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