RE: New 270.

["Andy Nolen-Parkhouse" <aparkhouse@xxxxxxxxx>]

Philipp,

My recollections are different.  I don't have a system with different
sized drives in the same ASP so I can't check.  If I understand what
you're describing, then all drives should have the same amount of data
measured in GB.  My thought is that they would have the same per cent
utilization regardless of capacity.

Does anyone out there have a reasonably stable system with multiple
drive sizes in the same ASP?  What are the characteristics of the ASP?
Per cent utilization per drive as compared to per cent utilization of
the ASP as a whole?

Regards,
Andy Nolen-Parkhouse

> -----Original Message-----
> From: midrange-l-admin@midrange.com
[mailto:midrange-l-admin@midrange.com]
> On Behalf Of Philipp Rusch
> Sent: Monday, June 03, 2002 2:26 PM
> To: midrange-l@midrange.com
> Subject: Re: New 270.
>
> Andy,
> I think to remember that the system is worse than you described:
> mixing 8 GB and 17 GB drives results in half the percentage on the 17
GB
> compared to the 8 GB drives, because an arm is an arm and the
controller
> does not know about the capacity "behind" this arm.
> So, if you you got a system with, for instance, 46 % used space on an
> 80 GB ASP consisting of 4x 8 GB (RAID5) and 4x 17 GB (RAID5)
> then the drive sets would look something like:  70 % space occupied on
> the 8 GB and 35 % used space on the 17 GB drives.
> This is only different when running ASP balancing or doing bulk
> unloads / reloads for large amounts of data.
> Generally speaking, I think one can much more easily overload a
certain
> disk arm with drives of higher capacity than with a bunch of smaller
> drives.
> I would certainly be interested in the exact algorhythms behind these
> symptoms I watched on real systems out there.
>
> Regards from germany, Philipp Rusch