RE: More disk arms myth exploded...

[Steve Morrison <smorrison@xxxxxxxxxxxxx>]

The SPD bus is a major performance drag.  We just replaced the drives in our
720. Since we had 4 parity sets, we pulled a drive from each parity set and
slipped in the replacement. This was using all 6714 drives, shipped from
Rochester. The drives on the SPD bus took 4 - 5 hours to rebuild parity, but
the drives on the PCI bus took 2.5 - 3 hours to rebuild parity. 

Steven Morrison
Beacon Insurance 
940-720-4672

-----Original Message-----
From: Jones, John (US) [mailto:John.Jones@xxxxxxxxxxxxxxxxxxxxxxx] 
Sent: Friday, August 13, 2004 2:10 PM
To: Midrange Systems Technical Discussion
Subject: RE: More disk arms myth exploded...

There aren't any LVD controllers for SPD systems so I had to go HVD.
Did the same on the 830 to keep the ability to move drives around in an
emergency.

We're looking at upgrading to 570s for both systems and if/when we do I'll
get the new 2780 DASD controllers and the new (forget the FC) tape
controllers.  And will swap the 3580s for LVD versions.  No use for fiber
here.  Will also standardize on 70GB 15K disks for both system; about 50 to
replace the 65 17GB disks in the current systems.  IBM modelled it and said
the workload should be do-able in 23-26 arms, but I'm not willing to reduce
the arm count that drastically.  (Besides, if I _have_ to get the 5094 I may
as well fill it up.)  I'm not sure what I'll do with 3+TB DASD, although I'm
sure the users will find a way to fill it eventually.

John A. Jones
Americas Security Officer
Jones Lang LaSalle, Inc.
V: +1-630-455-2787 F: +1-312-601-1782
John.Jones@xxxxxxxxxxxxxxxxxxxxxxx

-----Original Message-----
From: Glenn Ericson [mailto:Glenn-Ericson@xxxxxxx]
Sent: Friday, August 13, 2004 1:58 PM
To: Midrange Systems Technical Discussion; 'midrange-l@xxxxxxxxxxxx'
Subject: RE: More disk arms myth exploded...

John  the H23 is the HDV  model. Try the L23 and the LDV controllers- 
it  can   near match the speeds of  fiber . For  DASD  controllers  try 
the  new 2780  controller over the  2757  with 1GB  read cache and757MB
write cache.  Another item was  a mix of several different DASD sizes and
rpm rates, which is not  a performance plus.

Frankly,  in a production system, I'd be challenged to cut back to 16% of
the  original arms and expect continued performance as  those  bigger drives
begin to fill  with  data  or trash.


>-----Original Message-----
>date: Fri, 13 Aug 2004 10:49:01 -0500
>from: "Jones, John (US)" <John.Jones@xxxxxxxxxxxxxxxxxxxxxxx>
>subject: RE: More disk arms myth exploded...
>
>
>I would guess #1: Tape controller.  On our 730 using 3580-H23 drives, 
>saves at 70GB/hour over a 6534.  On our 830 using the same drive types 
>but a 2729, we get 200GB/hour.  The machines have similar RAM, CPW, # 
>disk arms, etc.  And really, more than the tape controller it's the SPD

>bus.
>
>You could also potentially mention the spreading of the data will be 
>optimal on the 520 as it was a reload. But I don't think it would make 
>that large of a difference.
>
>John A. Jones
>Americas Security Officer
>Jones Lang LaSalle, Inc.
>V: +1-630-455-2787 F: +1-312-601-1782
>John.Jones@xxxxxxxxxxxxxxxxxxxxxxx


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