Ide performance (was RAID0 Performance problems)

From: Andreas Peter (ujq7@rz.uni-karlsruhe.de)
Date: Sun Apr 15 2001 - 14:08:04 EST


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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This archive was generated by hypermail 2b29 : Sun Apr 15 2001 - 21:00:24 EST