[prev in list] [next in list] [prev in thread] [next in thread] 

List:       aix-l
Subject:    Re: Best Practice for Paging spaces - rootvg or not
From:       Mark J Ray <raym () US ! IBM ! COM>
Date:       2012-02-02 14:24:15
Message-ID: OFECA885D7.26D4F707-ON85257998.004E70DD-85257998.004F200D () us ! ibm ! com
[Download RAW message or body]

The simple answer on how to handle paging is: "Don't do it."

Look at it this way: In any environment -- I don't care HOW much memory you
have installed -- if you're
doing more than a few gigabytes worth of paging, you're in serious trouble.
In fact, what I tell clients with
large memory AIX systems, is that if they see paging to the tune of triple
digits in their vmstats, it requires
investigation.

So how much? Take the size of your non-mirrored rootvg image and start
there. If you need more paging
space than that *because* you're paging, then you need tuning, or
application/database optimization, and
an evaluation of what's causing the paging.

Best Regards,

Mark J. Ray
Infrastructure Architect
AIX Performance
Global Technology Services
IBM
email:  raym@us.ibm.com





From:	Andrew Townsend <Andrew.Townsend@ASCENSUS.COM>
To:	aix-l@princeton.edu
Date:	02/02/2012 09:15 AM
Subject:	Re: Best Practice for Paging spaces - rootvg or not
Sent by:	IBM AIX Discussion List <aix-l@princeton.edu>



This is some very good food for thought. We are getting ready to add memory
to a Sybase server which already has 128 GB of memory in a single LPAR. Our
configuration is a well tuned environment and at this time we only have 16
GB of paging space in the system.

We are getting ready to add another 128 GB of memory (for a total of 256
GB) and are reviewing our paging space and tunables again.

Any input from anyone on a "modern" way to handle paging space would be
much appreciated.

Andrew Townsend
Director of IT: Mid Range Systems/Storage
Office: (215) 648-8304  Fax: (215) 648-1268
Email: andrew.townsend@ascensus.com

Ascensus
200 Dryden Road
Dresher PA 19025
Visit us on the web at www.ascensus.com
People Matter. Quality First. Integrity Always



From: IBM AIX Discussion List [mailto:aix-l@Princeton.EDU] On Behalf Of
Christopher Baker
Sent: Wednesday, February 01, 2012 6:33 PM
To: aix-l@Princeton.EDU
Subject: Re: Best Practice for Paging spaces - rootvg or not

Funny that this topic has come up.  We have not spoken of guidelines on
paging space for a good while here where I work, but it recently raised its
head in a big way.

The questions here are:

1) How much paging space?  1x memory? 2x memory? 0.5x memory? Zero paging?
        - Came up because we have so much memory that paging space could
mean having to add multiple drives.

2) Where to put it?
        - This came up because we just put in LPARs that have No local
disk.  Even hdisk0 (rootvg) is a LUN off of our corporate EMC farm.
        - On that same note, we could ask for many, small, LUNs for
"improved" paging, but a LUN, be it small or large, is not a real disk, so
           spreading paging over four hdisks, when some or all are LUNs and
those LUNs each could be spread over 1 or 100 real disks/spindles, yet
           all come through the same Fiber Channel adaptor kind of turns
all the old paging rules/guidelines on their head, no?

My other question would be are Paging Guidelines true for different flavors
of UNIX and Linux as they are for AIX?  Are they even true for AIX 7.1 as
they were for AIX 5.2?

Just food for thought.

Chris Baker





From:        Mark J Ray <raym@US.IBM.COM>
To:        aix-l@Princeton.EDU
Date:        02/01/2012 01:43 PM
Subject:        Re: Best Practice for Paging spaces - rootvg or not
Sent by:        IBM AIX Discussion List <aix-l@Princeton.EDU>




Dave:

The default paging scheme in AIX is called "Deferred" (there are two
others: Early and Late). As such, paging occurs
in a round-robin fashion, meaning that, if you have more than two paging
spaces, AIX will put a page of data on paging
space A first, the next page on paging space B, etc... so you can see that
having more and smaller paging spaces on
as many disks is better than having one big paging space on a single disk.

It doesn't matter much if the paging spaces are located in other volume
groups, as long as they're located on different
disks, preferably which hang off of different fiber/scsi/whatever storage
adapters.

But really, you should try to eliminate paging from your system; heavy
paging is usually a sign of either a bad application
or an untuned system, so I might start with gathering statistics and seeing
if you do indeed need to configure paging
spaces over and above the AIX default.

Best Regards,

Mark J. Ray
Infrastructure Architect
AIX Performance and Diagnostics
Global Technology Services
IBM
email:  raym@us.ibm.com





From:                 "Miller, Dave (I.S.)" <Dave.Miller@BAYSTATEHEALTH.ORG
>
To:                 aix-l@princeton.edu
Date:                 02/01/2012 12:52 PM
Subject:                 Best Practice for Paging spaces - rootvg or not
Sent by:                 IBM AIX Discussion List <aix-l@princeton.edu>



Does anyone know where a best practice doc is that talks about whether
additional (after hd6) paging space LVs should be in rootvg, or another
volume group? i.e. if I need a 100GB paging space and have four 73GB disks,
do I make the second two disks for the paging LVs in rootvg, or make
another VG?
Thanks.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Dave Miller
IT Infrastructure Architect
Baystate Health
3601 Springfield, MA 01109 dave.miller@bhs.org
413-794-3836

"We can't solve problems by using the same kind of thinking we used when we
created them." Albert Einstein.




Please view our annual report at http://baystatehealth.org/annualreport


CONFIDENTIALITY NOTICE: This e-mail communication and any attachments may
contain confidential and privileged information for the use of the
designated recipients named above. If you are not the intended recipient,
you are hereby notified that you have received this communication in error
and that any review, disclosure, dissemination, distribution or copying of
it or its contents is prohibited. If you have received this communication
in error, please reply to the sender immediately or by telephone at
413-794-0000 and destroy all copies of this communication and any
attachments. For further information regarding Baystate Health's privacy
policy, please visit our Internet site at http://baystatehealth.org.


CONFIDENTIALITY NOTICE: This message is intended to be viewed only by the
listed recipient(s). It may contain information that is privileged,
confidential and/or exempt from disclosure under applicable law. Any
dissemination, distribution or copying of this message is strictly
prohibited without our prior written permission. If you are not an intended
recipient, or if you have received this communication in error, please
notify us immediately by return e-mail and permanently remove the original
message and any copies from your computer and all back-up systems.
[prev in list] [next in list] [prev in thread] [next in thread]