[275] in Enterprise Print Delivery Team
Re: MIT Configurations
daemon@ATHENA.MIT.EDU (jeffbant@us.ibm.com)
Tue Jun 6 10:11:40 2000
From: jeffbant@us.ibm.com
To: printdel@MIT.EDU
Cc: Philp_Muolo@us.ibm.com
Message-Id: <872568F6.004D772D.00@d53mta03h.boulder.ibm.com>
Date: Tue, 6 Jun 2000 10:06:07 -0400
Mime-Version: 1.0
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This note is in response to availability of RAID and dual power supplies on
the InfoPrint Manger hardware server. Through notes to Boulder and the
AIX support center it appears the 7044-270 is the best hardware for MIT's
intended use of IPM. It offers early entry in product life cycle and is
very expandable in dasd, processors, and memory. I will forward, other
notes and a final proposed configuration from the AIX Support Center
shortly. jb
******************************************************************************************************
Jeff Banta
IBM Printing Systems Division
404 Wyman St.
Waltham, Ma. 02454
8-362-2295 / 781-895-2295
fax 734-448-5932
mobile 617-513-5400
internet jeffbant@us.ibm.com
---------------------- Forwarded by Jeff Banta/Waltham/Contr/IBM on
06/06/2000 09:48 AM ---------------------------
To: Jeff Banta/Waltham/Contr/IBM
cc:
From: Steve Lawton/Providence/IBM@ibmus
Subject: Re: MIT Configurations (Document link: Jeff Banta)
JB,
Raid is available on the 270. Basically, SSA does not really imply RAID as
you can have SSA disk drives in a non-RAID environment, or using a SCSI
RAID Adapter, you can RAID SCSI Drives. SSA is just a faster technology
than SCSI. Also, internal disk mirroring, done at the AIX level, is
available on all of our RS/6000's and is considered to be RAID-0. RAID is
something that is set up at install (usually by either an IBM CE or the
Customer System Administrator). The RAID arrays are set up at the AIX
level. Following this note is some info on RAID definitions and how it
works. As for dual power, that is not available on the 270. If they have
power concerns, they may want to add a UPS to the system? I hope this
helps. I'll be around to help out with this one if you need it, just drop
me a note or give me a call. Thanks.
Support of concurrent striping and mirroring (RAID 0 + 1) provides a
software solution to what used to require unique hardware support.
This allows the performance advantages of striping to be combined
with the reliability advantages of mirroring.
STRIPING AND MIRRORING
The Logical Volume Manager (LVM) combines RAID 1 (mirror) data availability
with RAID 0 (striped) performance by supporting (entirely in software) a
striped logical volume with mirrors. This feature further enhances data
availability in high performance striped logical volumes by tolerating disk
failures. The remaining disks in the striped mirror copy continue to
service
striped units contained on these disks. The replacement of a disk where
only
the partitions on the new disk are synchronized is provided through the
migratepv or replacepv command.
There are a few RAID levels that describe different things. Some RAID
levels
are for performance, some are for high availability.
RAID 0 covers writing the same data to two identical disks. If one fails,
the other one picks right up.
RAID 1 covers writing alternate bytes to two identical disks. If one
fails,
you lose all your data, but since writing data to the drive is a relatively
slow process, you (theoretically) double the access to your drives.
RAID 2, 3, 4 aren't used much, but cover things like separate parity disks
to
rebuild a failed drive. If one drive fails, you're okay, but if the
parity disk fails, it's gone.
RAID 5 is probably the most popular, since it gives a great balance of
HA and performance. For N disks in your system, you get N-1*(size of
drive)
space available. In my RAID 5 configuration, I have three 4.5 GB drives,
which gives me a total space of 9.0GB. The missing 4.5GB is filled with
parity and ECC data to allow the entire system to run if one drive fails.
If two fail, you're sunk. Since data is scattered among all the drives,
you get a great thruput of read and write.
Steve Lawton
RS/6000 Advisory Sales Specialist
IBM Corporation
781-895-2878 -- T/L 362-2878 -- slawton@us.ibm.com
