In the last episode (Jan 22), Noah Garrett Wallach said:
> can somebody give me a better understanding of what the iostat output
> is decribing in the KB/t column. It might be really simple but
> figured I';d ask, if in fact further clarification can be given.
>
> typhoon% iostat 1
> tty da0 da1 acd0
> tin tout KB/t tps MB/s KB/t tps MB/s KB/t tps MB/s us ni sy in
> 0 21 0.00 0 0.00 0.00 0 0.00 0.00 0 0.00 1 0 1 0
>
> do drive specifications generally contain KB/t information or statistics?
When there is disk activity, yes. Try running a couple du's or extract
a couple ports, then run iostat in another window.
> I currently have an IDE drive that has the capacity to do 128KB/t and
> a SCSI drive 64KB/t. Are these stats in fact showing me that there
> is a limitation with the SCSI drive? Are my file transfering
> capaibilities less with the SCSI drive? I suppose what do I need to
> look for in the spcifications when choosing new drives so this does
> not happen again?
FreeBSD's SCSI layer has a cap of 64k per transaction (apparently
because ancient ISA adapters could not do more than 64k), and the ATA
layer has a cap of 128k. You won't see a difference using regular
disks. A 20MB/sec transfer rate comes out to ~300 64K
transactions/sec, which most systems should be able to handle with no
problems.
--
Dan Nelson
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