You can get write cache on the SSA RAID adapters as well.  Wouldn't they
provide the same type of performance benefit that ESS write cache does?  In
any event, the question that Mike originally asked was about Read
performance, not Write performance.

At 10:00 AM 11/5/2001 -0800, Joshua S. Bassi wrote:

The ESS is a whole different beast.  Because of the amount of cache
involved and the fact that the ESS provides write responses as soon as
data goes into the cache (and not actually written on disk) makes the
RAID-5 array on the ESS a superb storage pool for TSM backup data.


--
Joshua S. Bassi
Independent IT Consultant
IBM Certified - AIX/HACMP, SAN, Shark
Tivoli Certified Consultant- ADSM/TSM
Cell (408)&(831) 332-4006
jbassi AT ihwy DOT com

-----Original Message-----
From: ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU] On Behalf Of
Bill Mansfield
Sent: Monday, November 05, 2001 9:56 AM
To: ADSM-L AT VM.MARIST DOT EDU
Subject: Re: TSM Server 4.1.3 Performance

Unless your storage device is heavily cached, like IBM ESS or the other
big
storage boxes.
There is no way to avoid Raid 5 on ESS, and there is no way to avoid
Raid 1
on EMC Symmetrix.


_____________________________
William Mansfield
Senior Consultant
Solution Technology, Inc




                    "Joshua S.
                    Bassi"               To:     ADSM-L AT VM.MARIST DOT EDU
                    <jbassi@IHWY.        cc:
                    COM>                 Subject:     Re: TSM Server
4.1.3 Performance
                    Sent by:
                    "ADSM: Dist
                    Stor Manager"
                    <ADSM-L AT VM DOT MA
                    RIST.EDU>


                    11/05/2001
                    11:42 AM
                    Please
                    respond to
                    "ADSM: Dist
                    Stor Manager"






I would not recommend using RAID-5 for your disk storage pool unless it
is the only copy of the data and you cannot afford to use plain
mirroring.  TSM uses it's own striping technique for one and for two
RAID-5 has a sever write penalty associated with it.


--
Joshua S. Bassi
Independent IT Consultant
IBM Certified - AIX/HACMP, SAN, Shark
Tivoli Certified Consultant- ADSM/TSM
Cell (408)&(831) 332-4006
jbassi AT ihwy DOT com

-----Original Message-----
From: ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU] On Behalf Of
Mike Wiggan
Sent: Sunday, November 04, 2001 11:20 PM
To: ADSM-L AT VM.MARIST DOT EDU
Subject: TSM Server 4.1.3 Performance

Hi Guru's

I have recently installed a new TSM 4.1.3 server on a P600 and AIX
4.1.3. I
have 2*75Gybyte RAID5 Disk Cache attached through SSA. The performance
for
reading from disk to tape is fine for small files, but I only get
2.5MB/Sec
when files are larger than say 1Gbyte. I have set "SELFTUNETXNsize
Yes",
and it brought it up tothis speed when using two drives.

I have 18 *4Gbyte files on each RAID5 and can see that the data is
evenly
distributed in each file. I can see that the file say 7Gbytes is spread
throughout many of the Disk Storage Volumes. I don't want to go straight
to
tape as this causes a huge headache in scheduling.

Is this a known bottleneck or is there a way around to get at least
20MB/Sec?

Kind Regards
Mike Wiggan, TCS/31
Infrastructure Integration Specialist
Petroleum Devlopment Oman LLC
(michael.ma.wiggan AT pdo.co DOT om)

--
Paul Zarnowski                         Ph: 607-255-4757
Paul Zarnowski                         Ph: 607-255-4757
747 Rhodes Hall, Cornell University    Fx: 607-255-8521
Ithaca, NY 14853-3801                  Em: psz1 AT cornell DOT edu