Hi,
I'm using 2.2.14pre12 with the unified IDE driver (to get UDMA on PIIX)
and with raidtools and raid from 19990824 (the newest I've found).
Mainboard is an older LX based from Gigabyte with on board SCSI,
Processor PII233, RAM 64MByte. Primary harddisk an SCSI IBM, then I
added two new Maxtor IDE with each 27GB/7200rpm, which give me about
19MByte/s each (hdparm3.6). **Each disk is as a master on a seperate
channel.** Only the IDE disks are used in the raid0/raid1 setup, nearly
no system acivity, and definitly nothing on the IDE disks which are
right now only used to get the raid setup working right.
The problem:
using raid0 gives me a read/write performance of 20..23MByte/s, using
raid1 (reading) gives only 9MByte/s (hdparm). Checking with dd to
read/write a 200MByte file it shows that raid1 reading is only as fast
as raid1 writing is, which is definitly not the expected value
(dd if=/dev/zero of=/mnt/raid1/tempfile count=409600 to write
and dd if=/mnt/raid1/tempfile of=/dev/null count=409600 to read)
I've checked in the mail archive (which I've found only available until
Aug99) and set the chunk size to 128 as suggested there. As a result
the performance while rebuilding the mirror in the background came up
to more than 20MByte/s (e.g. reading big chunks from only one disk), but
once the reconstruction was done it fell down to 9Mbyte/s again.
To make sure that it utilizes both disks in reading I've checked the
stats of IRQ 14 and 15 (the both IDE channels, check done with sar from
the sysstat-2.2 package) and it shows that **both** channels are used
at about 75 interupts per second and channel (cpu usage system around
20%) while reading from the raid1, compared to 160 interrupts per second
and channel (cpu usage system around 40%) when reading from the raid0.
Any ideas?
Any help appreciated.
Steffen
