Re: Raid 5 or 0?

Using the list archive, search on RAID or on my name.  I've written about
the perils of RAID 5 in a TSM environment a number of times.  There is a
white paper on our website that discusses SDLT vs. LTO tape performance and
in there is a discussion about RAID5 as well.  Something I learned during
the performance testing.

Kelly J. Lipp
STORServer, Inc.
485-B Elkton Drive
Colorado Springs, CO 80907
lipp AT storsol DOT com or kelly.lipp AT storserver DOT com
www.storsol.com or www.storserver.com
(719)531-5926
Fax: (240)539-7175


-----Original Message-----
From: ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU]On Behalf Of
PINNI, BALANAND (SBCSI)
Sent: Tuesday, November 12, 2002 7:59 AM
To: ADSM-L AT VM.MARIST DOT EDU
Subject: Re: Raid 5 or 0?


How about Raid0+1 .
That is performance and availability.

Balanand Pinni
SBC Services Inc.
Work:314-206-5911
Pager:1-800-451-6897
Email ID :bp3965 AT momail.sbc DOT com
8004516897 AT mobilecomm DOT net e.mail pager





-----Original Message-----
From: Gianluca Perilli [mailto:Gianluca_Perilli AT IT.IBM DOT COM]
Sent: Tuesday, November 12, 2002 4:44 AM
To: ADSM-L AT VM.MARIST DOT EDU
Subject: Re: Raid 5 or 0?


Choosing RAID5 is a good solution if you have data heavily accessed in a
read mode: in fact in this case you don't face the performance problem of
the parity calculation/writing: for example choosing it for the TSM DB it
is not a bad idea; furthermore RAID5 is more effective in the usage of the
disk space.
The RAID 0 is a good choice whenever you want high performances because you
can leverage the data spreading on multiple disks and you don't have to
calculate any parity: however if you have a  problem on a disk you loose
all your data because the system cannot re-build these data as no parity
exists. Then, if you want good performances without incurring in problems
of lost data, it is better to think about RAID10, ie a RAID0 mirrored to
another RAID0 array: the performances and security are the highest, but
unfortunately the disk space usage too.
So RAID10 is a good choice for the heavily written data, like for example
the Recovery log in TSM.
Hope this helps.

Cordiali saluti / Best regards

Gianluca Perilli

EMEA Support, GlobalResponseTeam Storage
e-mail: gianluca_perilli AT it.ibm DOT com

Tivoli Software, IBM Software Group

Via Sciangai 53, Rome 00144            Italy
Office : +39.06.59664581
Mobile: +39.335.7840985
Fax:      +39.06.59662077






                      Luke Dahl
                      <ldahl AT JPL DOT NASA.G        To:
ADSM-L AT VM.MARIST DOT EDU
                      OV>                      cc:
                      Sent by: "ADSM:          Subject:  Raid 5 or 0?
                      Dist Stor
                      Manager"
                      <[email protected]
                      .EDU>


                      11/11/2002 11:07
                      PM
                      Please respond to
                      "ADSM: Dist Stor
                      Manager"





Hi,
    We're considering changing from RAID5 to RAID0.  Info:
Solaris 5.8
TSM Server 4.2.1.15
Storage array 21 36Gb disks (currently RAID5.

Is this a wise move?  If we make the change, any recommendations on the
stripe setting?  Default is 64Kb, but it can be set while we
configure...  Performance seems quite slow with RAID5 and we have  a
development box we're going to throw this at.  Any thoughts or
recommendations are much appreciated.

Luke Dahl
NASA - Jet Propulsion Laboratory
818-354-7117