RE: 2757 Controller Card

Battery backup, yep.

The reason for the backup card (the 5580/5580b combo) is to prevent
against failure of the cache itself.  A battery is designed for keeping
data in cache memory during a failure of the system which prevents the
write to disk during a planned shutdown.  But that controller card
failing - no battery can help you there.  =)  That's why the second card
keeps an extra copy of the cache in case the primary card fails.  It
won't keep the system online, but it will allow you to recover that
cache data once you replace the primary disk controller.

Now - the 2757 you mention also has a backup card (5581/5581b combo),
but the 2757 itself is lacking the 1GB read cache of the 2780.  That
makes a huge diff in performance.

Hope that helps.


--
Justin C. Haase - iSeries System Engineer
IBM Certified Systems Expert - System i
Kingland Systems Corporation

-----Original Message-----
From: midrange-l-bounces+justin.haase=kingland.com@xxxxxxxxxxxx
[mailto:midrange-l-bounces+justin.haase=kingland.com@xxxxxxxxxxxx] On
Behalf Of Ryan Hunt
Sent: Tuesday, July 18, 2006 9:47 AM
To: midrange-l@xxxxxxxxxxxx
Subject: Re: 2757 Controller Card

Thanks for that link.  I'm curious about your statement "I'd recommend
the 2780 with cache backup - if you lose that much cache in a failure,
you're basically guaranteed a reload."

I thought the 757MB write cache on the 2757 was battery backed.  It is,
right?

"Haase, Justin C." <justin.haase@xxxxxxxxxxxx> wrote in message
news:898A55683B5A5E4C8071CE2960E1E2B201B8AC06@xxxxxxxxxxxxxxxxxxxxxxxx

The redbook knows.  There's charts inside.

www.redbooks.ibm.com - search for System Builder

When you read that redbook, there's charts about specific disks which 
answer some of your query - however, not sure where you'd find an 
official "I/O per second sustained" number.  The more cache the

better.

I'd recommend the 2780 with cache backup - if you lose that much cache

in a failure, you're basically guaranteed a reload.
---------

The #2757 PCI-X Ultra RAID Disk Controller is an Ultra SCSI disk unit 
controller with a 757 MB compressed maximum cache that provides RAID-5

protection for internal disk units. It also supports up to two 
internal tape devices, CD-ROM, and DVD units. The #2757 has four Ultra

SCSI buses.
The #2757 is not supported in the system unit of Models 520, 550, 570,

or 595.
A minimum of three disk units of the same capacity is needed for a 
valid
RAID-5
configuration. A maximum of six arrays is allowed per controller, with

a maximum of 18 disk units allowed per array.

The #2780 PCI-X Ultra RAID Disk Controller is an Ultra4 (u320) SCSI 
disk unit controller with a maximum compressed write cache of 757 MB 
and a maximum

compressed read cache of 1GB that provides RAID-5 protection for 
internal disk units. It also supports up to two internal tape devices,

CD-ROM, and DVD units.
The #2780 has four Ultra4 SCSI buses.
The #2780 is not supported in the system unit of the Model 520, 550, 
570, or 595. Up to 20 disk units per #2780 are supported in a #5094 
PCI-X Expansion Tower attached to a Model 520, 550, 570, or 595.
A minimum of three disk units of the same capacity is needed for a 
valid
RAID-5
configuration. A maximum of six arrays is allowed per controller, with

a maximum of 18 disk units allowed per array.


--
Justin C. Haase - iSeries System Engineer IBM Certified Systems Expert

- System i Kingland Systems Corporation

-----Original Message-----
From: midrange-l-bounces@xxxxxxxxxxxx
[mailto:midrange-l-bounces@xxxxxxxxxxxx] On

Behalf Of Ryan Hunt

Sent: Tuesday, July 18, 2006 9:27 AM
To: midrange-l@xxxxxxxxxxxx
Subject: 2757 Controller Card

Anyone know how much data the 2757 Controller Card can handle?  Is it 
U320?
More importantly, how many I/O's per second can it sustain?



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