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

        Dan Nelson

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