Very Computer

1. Weird IDE performance issue with two IDE drives

Hi everyone,

I've been fruitlessly googling for days now trying to find an answer
to this issue, and have given up - so, following the advice in the
UDMA Mini-HOWTO, I'm posting this here :)

I have two IDE hard drives in my linux box, one is a Western Digital
Caviar WDC WD204BB, the other is an IBM Deskstar IC35L060AVER07-0.

I've been trying to use hdparm to get maximum performance out of both,
but so far, unsuccessfully.

Currently the WD is giving me buffered disc reads of ~25MB/s, but the
deskstar won't get much above ~6MB/s.

Here are the settings from hdparm for both drives :

Western Digital
/dev/hda:
 multcount    = 16 (on)
 IO_support   =  1 (32-bit)
 unmaskirq    =  1 (on)
 using_dma    =  1 (on)
 keepsettings =  0 (off)
 readonly     =  0 (off)
 readahead    =  8 (on)
 geometry     = 2482/255/63, sectors = 39876480, start = 0

IBM
/dev/hdc:
 multcount    = 16 (on)
 IO_support   =  1 (32-bit)
 unmaskirq    =  1 (on)
 using_dma    =  1 (on)
 keepsettings =  0 (off)
 readonly     =  0 (off)
 readahead    =  8 (on)
 geometry     = 7476/255/63, sectors = 120103200, start = 0

Once upon a time, both drives were on the same channel (i.e. as hda
and hdb) but someone suggested moving them to different channels to
see if it was the Master/Slave relationship that was the problem -
however, such does not appear to be the case - with much cursing I've
managed to recable everything into a working state inside the box so
that the drives are on different channels now.

IDE0 channel is also now sporting the DVD drive that used to be on
IDE1, and the CD-RW is still on IDE1 with the IBM now.

With this setup I get the following numbers (not run in single user
mode, so excuse me :) )

/dev/hda:
 Timing buffer-cache reads:   128 MB in  0.85 seconds =150.59 MB/sec
 Timing buffered disk reads:  64 MB in  2.75 seconds = 23.27 MB/sec

/dev/hdc:
 Timing buffer-cache reads:   128 MB in  0.88 seconds =145.45 MB/sec
 Timing buffered disk reads:  64 MB in 15.28 seconds =  4.19 MB/sec

Crappy huh ?

Anyone got any ideas?

FWIW, the hdc drive (the deskstar) is the drive with the OS installed
on it, /dev/hda is only mounted under /opt and contains all my mp3s
:)

Bry

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