ADSM-L

Re: SUSPECT: (MSW) Re: Advice needed for EMC CX500 setup

2005-06-08 11:39:25
Subject: Re: SUSPECT: (MSW) Re: Advice needed for EMC CX500 setup
From: PAC Brion Arnaud <Arnaud.Brion AT PANALPINA DOT COM>
To: ADSM-L AT VM.MARIST DOT EDU
Date: Wed, 8 Jun 2005 17:38:32 +0200
Richard,

This is what I call helpfull information ! It confirms what I read in
EMC's engineering white paper "Backup-to-Disk Guide with IBM Tivoli
Storage Manager", where they recommend using RAID3 for storage pools.
Unfortunately there was not any word about TSM DB and logs ...
As our Clariion is also equipped with 50TB SATA drives, I'll use them as
sequential type volumes  with raid3, and will give raid5 a chance on FC
drives, for primary disk pool where our nighly backups are landing
(hopefully it will not be too slow), for DB and LOGS too ...
Thanks.

Arnaud 

************************************************************************
******
Panalpina Management Ltd., Basle, Switzerland, CIT Department
Viadukstrasse 42, P.O. Box 4002 Basel/CH
Phone:  +41 (61) 226 11 11, FAX: +41 (61) 226 17 01
Direct: +41 (61) 226 19 78
e-mail: arnaud.brion AT panalpina DOT com
************************************************************************
******

-----Original Message-----
From: ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU] On Behalf Of
Richard Rhodes
Sent: Wednesday, 08 June, 2005 16:57
To: ADSM-L AT VM.MARIST DOT EDU
Subject: SUSPECT: (MSW) Re: Advice needed for EMC CX500 setup

At the recent EMC conference at a session about Clariions, they
indicated several things about Clariions that I thought I would share.
>From my notes . . . .

1)  Raid 0+1 is better for writes, but doesn't help with reads.  It will
only/mostly use just one copy for reads.  It's not as smart as a
dmx/symm, which will perform reads from both copies.  Raid 5 random
reads are just as good as 0+1 random reads.

2)  Raid 3.  The way I heard it explained, r3 was recommended for big
block sequential processing (like tsm staging pools) for ATA drives.
The reasoning was that ATA drives don't currently have command tag
queueing.  Since they can only do one i/o op at a time, r3 fits real
well with this.  They recommended this for up to around 10
concurrent data streams to the raidset.   The quote went something
like this:  ATA drives are brain dead, and raid 3 optimizes their
brain-deadness.

3)  Raid 5 on Fiber Channel drives is  very good with large block
sequential I/O.  Raid 3 is not needed here.

4)  Raid5 definitely has the write performance penality, which
requires 4 i/o's per random write (not writing a full strip).   This
is hidden behind the write cache and performed later.   They gave
a rule of thumb of using raid5 for random I/O up to a  write/read ratios
of around 25-30%.  That is, a random access pattern where there is 70%
reads and 25% writes.

5)  Leave the raidset strip size at the default (I think it's 64k, or
128 blocks).  They have performed all kinds of internal testing and this
is the optimum size for Clariion raid 5 raidsets.  Period.  The internal
processing logic of the Clariion is optimized for this strip size -
don't mess with it unless you reallllllly know what you are doing.

6)  15k rpm fc drives give around a 30% increase in small block random
iops than 10k drives.


Rick


-----------------------------------------
The information contained in this message is intended only for the
personal and confidential use of the recipient(s) named above. If the
reader of this message is not the intended recipient or an agent
responsible for delivering it to the intended recipient, you are hereby
notified that you have received this document in error and that any
review, dissemination, distribution, or copying of this message is
strictly prohibited. If you have received this communication in error,
please notify us immediately, and delete the original message.

<Prev in Thread] Current Thread [Next in Thread>
  • Re: SUSPECT: (MSW) Re: Advice needed for EMC CX500 setup, PAC Brion Arnaud <=