My guess at a glance would be either the Marvel driver is at fault, or
the simple fact of software raid performance... did you monitor the cpu
useage during the tests? even PCI 32bit, 33mhz should be able to hit
133 Mbytes per second I believe. What are you writing *from* ? dev/zero
or another drive that may not have a read speed high enough to keep up
with what is available?
Tyler.
Ming Zhang wrote:
I meet some strange low performance when run RAID0 with vanilla kernel
2.4.27/2.6.11.12.
My box is a 2.8G P4 and 1G RAM. 8 400GB SATA disk and A marvel 8port
controller. I run marvel 3.4.1 driver. I wrote a small program to write
device sequentially and SYNCHRONOUSLY.
This is performance of 1 disk. looks fine.
1048576Bytes * 1024 : 55.466MB/s
524288Bytes * 2048 : 55.830MB/s
262144Bytes * 4096 : 55.782MB/s
131072Bytes * 8192 : 55.567MB/s
65536Bytes * 16384 : 55.926MB/s
32768Bytes * 32768 : 54.344MB/s
16384Bytes * 65536 : 41.415MB/s
8192Bytes * 65536 : 26.499MB/s
4096Bytes * 65536 : 15.110MB/s
2048Bytes * 65536 : 8.422MB/s
1024Bytes * 65536 : 4.318MB/s
But when run 2 disk raid0, there is only 10% improvement.
md3 : active raid0 sdb[1] sda[0]
781422592 blocks 64k chunks
1048576Bytes * 1024 : 67.300MB/s
524288Bytes * 2048 : 66.796MB/s
262144Bytes * 4096 : 65.728MB/s
131072Bytes * 8192 : 65.017MB/s
65536Bytes * 16384 : 59.223MB/s
32768Bytes * 32768 : 49.766MB/s
16384Bytes * 65536 : 39.162MB/s
8192Bytes * 65536 : 26.386MB/s
4096Bytes * 65536 : 15.084MB/s
2048Bytes * 65536 : 8.383MB/s
1024Bytes * 65536 : 4.303MB/s
And when use 4 disks, the speed is slower!
md0 : active raid0 sdh[3] sdg[2] sdf[1] sde[0]
1562845184 blocks 64k chunks
1048576Bytes * 1024 : 58.032MB/s
524288Bytes * 2048 : 56.994MB/s
262144Bytes * 4096 : 58.289MB/s
131072Bytes * 8192 : 65.999MB/s
65536Bytes * 16384 : 59.723MB/s
32768Bytes * 32768 : 50.061MB/s
16384Bytes * 65536 : 38.689MB/s
8192Bytes * 65536 : 26.169MB/s
4096Bytes * 65536 : 15.169MB/s
2048Bytes * 65536 : 8.378MB/s
1024Bytes * 65536 : 4.287MB/s
Any hint on this?
* I do not know how to check current PCI bus speed and I am not sure
whether is limited by that. It is a 64bit card but I am not sure if it
is run at 66MHZ. Should be, but want to check to make sure.
* I tested each disk and all disk performs OK.
Thanks
Ming
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