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SubjectIde performance (was RAID0 Performance problems)
Date
Hi,
I've posted about performance problems with my RAID0 setup.
RAID works fine, but it's too slow.
But now it seems not to be a problem with the md code, it's an ide problem.
There are two HDs in my PC: /dev/hda and /dev/hdc. No other devices are
attached to the ide-bus.
PC is a SMP-System, 2 Celeron 533, Gigabyte 6BXDS with Intel BX-Chipset,
66MHz FSB.
The hdparm settings:

bash-2.04# hdparm /dev/hda /dev/hdc

/dev/hda:
multcount = 0 (off)
I/O support = 3 (32-bit w/sync)
unmaskirq = 1 (on)
using_dma = 1 (on)
keepsettings = 0 (off)
nowerr = 0 (off)
readonly = 0 (off)
readahead = 0 (off)
geometry = 59556/16/63, sectors = 60032448, start = 0

/dev/hdc:
multcount = 0 (off)
I/O support = 3 (32-bit w/sync)
unmaskirq = 1 (on)
using_dma = 1 (on)
keepsettings = 0 (off)
nowerr = 0 (off)
readonly = 0 (off)
readahead = 0 (off)
geometry = 59556/16/63, sectors = 60032448, start = 0

I've tested a lot of variations of this settings (multcount=16,
unmaskirq=0...) without succes.
The performance of the RAID doesn't increase :-(
hdparm -tT on a single HD (dev/hda3 is the RAID-partition) reports a very
good performance:

bash-2.04# hdparm -tT /dev/hda3

/dev/hda3:
Timing buffer-cache reads: 128 MB in 1.42 seconds = 90.14 MB/sec
Timing buffered disk reads: 64 MB in 2.27 seconds = 28.19 MB/sec

But if I start 2 hdparms simultanous (one on /dev/hda3 the other on
/dev/hdc3) the performance on the HDs decreases to 1/2 of the original speed:

bash-2.04# hdparm -tT /dev/hda3

/dev/hda3:
Timing buffer-cache reads: 128 MB in 2.27 seconds = 56.39 MB/sec
Timing buffered disk reads: 64 MB in 4.56 seconds = 14.04 MB/sec

bash-2.04# hdparm -tT /dev/hdc3

/dev/hdc3:
Timing buffer-cache reads: 128 MB in 2.25 seconds = 56.89 MB/sec
Timing buffered disk reads: 64 MB in 4.49 seconds = 14.25 MB/sec

The performance of the RAID0:

bash-2.04# hdparm -tT /dev/md0

/dev/md0:
Timing buffer-cache reads: 128 MB in 1.35 seconds = 94.81 MB/sec
Timing buffered disk reads: 64 MB in 3.11 seconds = 20.58 MB/sec

Tests with bonnie or iozone have the same reuslts, RAID is slower then a
single HD :-(

Does anybody has an idea what's wrong with my setup??

Thx,
Andreas
--
Andreas Peter *** ujq7@rz.uni-karlsruhe.de

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