Actually, what we are looking at is a SSA controller with 2 channels. Each
set of disks sits on its own channel. SSA has a much higher throughput and
higher number of operations per second. Plus it has the advantage of being
slightly cheaper than the equivalent SCSI solution from IBM. In addition SSA
has numerous other benefits, but I don?t want to sound like a salesman.

Paul Shields
pshields AT bnr DOT ca

In message " ADSM Experiences", ADSM-L AT VM.MARIST DOT edu writes:

>On Tue, 5 Sep 1995 13:00:00 -0500 paul (p.) shields said:
>>You should acheive maximum performance and uptime by mirroring two sets of
>>stripped volumes. You get all the write benefits of stripping and all the
>>read benefits of mirroring. Plus you never have any down time. When a
volume
>>fails you put a new one in and resynch the databases.
>
>>This is the configuration being recommended by IBM. The problems we are
>
>Well, I can see where that could give you good performance.   Going all
>out say two seperate RAID disk arrays with decent disk space, each w/4 2GB
>disks, you begin to talk some serious money though.  I guess just for
>kicks you could add a dual controller to each array as well.  What would
>all that cost ~$50K in IBM equipment?  Mucho dinero there.
>
>I would guess a poor man's solution to performance could be to spread the
>database over two plain FW/SCSI-2 disk arrays and mirror them, use some
>1GB sub-7ms read access disks to spread the database over the maximum
>number of spindles.  Since the 2GB drives are about 8ms you'd gain 12-15%
>increase for the average read but, I think the average write is the same
>about 9ms.  Even this solution would probably cost what, ~$25K.
>
>Price/performance issues can be such a pain sometimes.
>
>>having is that our backups have a very small average file size, thus
require
>>a lot of database activity and overhead during backup. What i want to
really
>>know is with an average file size of 20-40K what kind of performance are
>>other sites seeing? If performance is breaking 1500Kb/s, how is you system
>>configured to acheive this? We are seeing performance in the 500-1000 Kb/s
>>range and this is very dissapointing.
>
>---
>Keith A. Crabb         Keith AT UH DOT EDU
>University of Houston  Operating Systems Specialist +1-713-743-1530
>