27 Aug
2004
27 Aug
'04
11:18 p.m.
Malcolm Baldridge wrote:
While it's handy for extra storage to "fill
up" the master/slaves, the
performance is never good. It's especially bad because you have the
swap
device on the same IDE channel as another data storage device. Unlike
SCSI, IDE channels don't "overlay multiple i/o commands" or have
intelligent multiple outstanding I/O commands where the device
re-targets the host when
the I/O is completed. Furthermore, the "slave" device truly is a
second-class citizen, vis-a-vis contentious I/O access attempts.
Thanks for the detailed reply. I am not thinking this is a low level
problem. The setup, as is, has been working under Windows just fine, ie
the disk Mbytes/sec (up to ~17MB/s) and cpu utilization (a few %) for
streaming is the same for the two drives, so the Master-Slave
distinction does not seem to be important. With Cakewalk I can stream 8
stereo tracks off of the Slave drive without breaking a sweat.
hdparm gives pretty much identical results for the two drives
performance wise, going by your examples. They've been setup properly
at boot time. Cable is right, bios settings, etc etc...
It looks more like some kind of unecessary double buffering going on, as
if data from hdb is being written to swap (or some buffer) first, then
read from there by the application (XMMS or others).
This is with Mandrake 10, but I wouldn't think it would be specific to
that distro. I'm stumped. Seems like others would have run into this at
some point.
AC