Re: Squid on IDE

David J N Begley wrote:

> Speaking of which - does anyone know of a reasonably accurate
> mechanism for measuring channel/bus utilisation? This could be
> F/W SCSI on a SPARC running Solaris, or EIDE on a Pentium running
> Linux.

For SCSI is should be possible to measure this as total blocks / second
to and from all disks on that channel. If this is close to the SCSI bus
speed then you need another SCSI bus.

For EIDE the measure is much simpler. If the first drive is busy (high
I/O latency) then don't add a second drive on the same channel. Due to
the nature of EIDE Squid it can only utilize the speed of little more
than one drive on a single EIDE bus. The EIDE bus speed is not the
limitation here, the EIDE command structure is.

Solaris is fairly well instrumented for I/O measurement. See manpages on
sar and iostat.

I haven't found any tool on Linux that can give good I/O measurement.
Perhaps the kernel is not instrumented to measure I/O performance...

---
Henrik Nordstrom
Spare time Squid hacker