Re: Promise, DMA and RAID5 problems running 2.4.1

Stephen Wille Padnos
2001-02-08T02:11:45Z

"A.Sajjad Zaidi" wrote:

> > do you understand that you can't really have raid on ide involving
> > two drives on the same channel?
>
> Is that just because of performance or are there other problems? Its working
> fine as it is, but Im considering setting up all drives as masters (2x
> ATA-100, 2x ATA-66).

It's because IDE is a blocking bus - each drive must complete its' task before
the data bus is released for the next IO operation. So, the first drive will
finish writing to the disk before the second drive can start. (That's one
reason why SCSI is preferred for high end systems - you can "disconnect" from
an IO operation to allow other IO's to be sent to other devices on the same
bus)

--
Stephen Wille Padnos
Programmer, Engineer, Problem Solver
swpadnos@adelphia.net