Extremely poor disk performance on SCSI RAID
All,
I'm getting extremely low disk performance on my new server, and suspect I have some incorrect kernel options or hardware configurations. Troughput as follows: Code:
[189] SUPERUSER@spirou:/tmp#dd if=/dev/sda7 of=/dev/null bs=64k count=100 Some more system info: Code:
00:00.0 Host bridge: Broadcom CMIC-WS Host Bridge (GC-LE chipset) (rev 13) http://pastebin.ca/411667 dmesg output can be found here: http://pastebin.ca/411670 The server in question is an IBM x335 with an LSI Logic 53c1030 SCSI-RAID controller which has two Ultra320 SCSI disks in RAID-1 set up in hardware. Processor is Dual-XEON 2.4Ghz which gives 4 cores in 2.6 Linux kernels. Memory is 2Gb. Since these are 2x 10kRPM 36GB Ultra320 SCSI disks, something is clearly wrong given the ultra-low read and write data. Any insight on this would be more than greatly appreciated! -Y1 |
Try copying disk to disk - i.e. don't use /dev pseudo device, and see what your numbers look like then.
Edit: Ooops, missed the underlined bit above. I've seen similar numbers from using /dev/urandom to create test files. Copying them disk to disk gets "real" numbers. |
Hello, and thank you for responding.
I now did as you recommended and got even worse throughput: Code:
[495] root@spirou:/root#dd if=testfile.out of=/tmp/test.ttt bs=128k count=1000 Any further suggestions would be warmly welcome! -Y1 |
I have a quad zeon with hardware raid5, using Adaptec AIC7899 Ultra160 SCSI. Reboot shows my (initial) copy of 80-odd Meg at 8k blocksize getting (variously) 25-30 MB/s. Bumping it to 64k made no discernable difference.
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Could the problem perhaps be that I have compiled multiple SCSI-controllers into the kernel, so that they are competing for attention?
Have you compiled only the Adaptec-specific RAID driver, or have you also included the md/raid section? |
Couldn't say. In my case, this is an Arch build. i686 optimised, and it loads modules for the hardware it finds - guess it must have the AIC7999 or somesuch in the initrd as I don't recall having to rebuild it.
As it happens I have a test kernel I'm using for cpusets and resource container patch testing. It's all compiled in and as lean as I could sensibly make it. Testing that shows similar numbers. |
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