OK, so there seems to be some interest in how to layout disk pools on an
AIX system using JFS2 instead of raw lv's.  I will try to keep this as
general as possible so please remember you must make some choices based
on your particular environment.

   * In general I would rather have more small disks than a few large
     as you will see.  However, this would not apply if the larger disk
     where 15K rpm vs. smaller disks of 10K rpm.
   * Creating your hdisks - there are several possibilities here
     depending on you environment.
         o Small environments with only a few disk should use JBOD.
           obviously you give up some safety over running RAID 1, 5 or
           10 but small environments can't afford this anyway.
         o Mid size and above should use one of the following configs
           that fits there environment the best.  If you will use RAID
           5 then create several small arrays, 4 or 5 disks per array
           is good if you have lots of disk then you can go as high as
           8 per array.  If you have a very large number of disks than
           you can use either RAID 0 or 10, obviously RAID 10 will give
           you some disk failure protection but at the cost of 2 x
           actual space vs. usable space.  Again 4 or 5 disk arrays (8
           or 10 if RAID 10) will work well and as before you can go
           larger if you have a very large number of disks to work with.
         o The idea of using small arrays is so that you wind up with
           as many hdisk's as possible.  I like to have at least 4 or
           5, but I have also worked in environments with over 50
           hdisks each of which was a RAID array.
         o NOTE: This section assumes you are not using any disk
           virtualization.  In virtualized environments you could have
           logically created 4 disk arrays but physically they might
           all be on the same set of disks.  That situation could cause
           some performance issues.  Disk virtualization is way outside
           the scope of this note.
   * Create a VG from all the hdisks above, nothing tricky here.
   * Create a JFS2 large file enabled file system on each disk.  Make
     sure the file system consume the entire hdisk and that it does not
     span multiple disks.  Any reasonably skilled AIX admin can do this
     for you.  In regards to the log file for these file systems for
     absolute maximum performance you could dedicate a separate disk to
     handle the logs, but in most cases simply selecting "in line" log
     will do fine.
   * NOTE: This is very important make sure that you add the mount
     option of RBRW to each of these file systems.  Also, it would help
     to add this mount option to the file systems that contain your
     ITSM DB and LOG.  This option increases the I/O performance and
     reduces the load on the system.  You will also see a radical
     reduction in system non-computational memory usage.  Which means
     you can use more memory for DB and LOG pages as well as for
     network performance.  For a more in depth discussion of this
     option please refer to the AIX Performance Management Guide.
   * Now create the storage pool volumes.  The size of these volumes is
     somewhat up to you, but I like to make sure that I have at least
     as many volumes as I might have backup sessions writing to this
     disk pool at any given time.  That is because each backup session
     (remember a client could have multiple session) opens a volume for
     its exclusive use.  Therefore if I have enough volumes they can
     all run at once.  NOTE: Again this is very important, when you
     create your volumes for the storage pool make sure you use a round
     robin approach to using the hdisks, i.e. if you have 10 hdisks
     then create the first on hdisk1, second on hdisk2, third on
     hdisk3, and so on so that 11th would be back on hdisk1.  And you
     must create them in sequential order!  The reason for this is that
     ITSM appears ( I have never seen the code nor have I had any
     developers confirm this, although they all agree it appears to do
     this) to use the volumes in the order they were created.
     Therefore, I am sure that once a backup starts I will get all of
     my hdisks in the game and the same thing will apply on migration.
   * Some simple tunable system parameters, please note that when you
     begin to do performance tuning you should know what you are doing
     if you don't then get someone that does because you can cripple a
     system if you are not careful.  Having said that, you should
     definitely adjust the min/max read ahead values
     (j2_minPageReadAhead and j2_maxPageReadAhead) with the ioo command
     a good starting point is 16/128.  If you use the RBRW on the file
     systems you won't need to make changes to minfree and maxfree
     despite what some of the literature says you need do when you
     increase the page ahead value.  Minperm and maxperm parameters
     have been talked about on lot on this list, but again if you are
     using the RBRW mount option these values will have a marginal
     effect since most of your non-computational memory usage will be
     released immediately (without the use of the LRU).  However, it
     won't hurt any if you lower maxperm to 60% with the vmo command so
     that you make sure that you have plenty of memory for
     computational pages, i.e. ITSM DB and LOG pages as well as network
     memory usage.
   * One area of tuning that I can't cover here is tuning the path to
     your disk and tape drives.  There is just to many combinations
     possible (SSA, SCSI, FC, iSCSI, etc.) to give any input.  However
     it is important that you address the performance issues of these
     various communication paths.  I will mention a couple of common
     problems.  Make sure that you don't overload you particular bus
     technology, i.e. you can't  put 6 LTO1 drives on the same SCSI
     bus.  So make sure you know the bandwidth of you bus and don't
     overload it!  Another common mistake is in FC environments, don't
     have disk I/O traffic and tape I/O running over the same HBA this
     just causes horrible performance and there is no amount of tuning
     that can fix it!  You must use separate HBA's and zone your switch
     to make sure that traffic stays separate.  SSA loops should have
     at least 4 initiators, i.e. use at least 2 SSA cards on each loop,
     and make sure that the SSA cards are connect as far away from each
     other in the loop as possible.
   * Some ITSM tunables. for the ITSM DB and LOG pages make sure you
     have set BufPoolSize and LogPoolSize large enough so that you are
     getting at least 99% Cache Hit Pct. on the DB and that your Log
     Pool Pct. Wait is 0.  Your MoveBatchSize and MoveSizeThresh should
     be set to the max values, this will help things like migration and
     storage pool backups.

This is a very general list of things you can do, but if you take these
guidelines and apply some common sense about your particular environment
I am sure that you can get very good performance out of your disk/tape
subsystems.

If you have any questions or comments on this than post them and lets
keep this discussion going.

--
Regards,
Mark D. Rodriguez
President MDR Consulting, Inc.

===============================================================================
MDR Consulting
The very best in Technical Training and Consulting.
IBM Advanced Business Partner
SAIR Linux and GNU Authorized Center for Education
IBM Certified Advanced Technical Expert, CATE
AIX Support and Performance Tuning, RS6000 SP, TSM/ADSM and Linux
Red Hat Certified Engineer, RHCE
===============================================================================



Wells, William wrote:

I would be interested in your post.

-----Original Message-----
From: Mark D. Rodriguez [mailto:mark AT MDRCONSULT DOT COM]
Sent: Sunday, November 14, 2004 5:49 PM
To: ADSM-L AT VM.MARIST DOT EDU
Subject: Re: TSM and SATA Disk Pools


Charles,

I may be missing something here, but even your numbers out of the
Symetrix seem pretty bad.  Are you sure you didn't drop a "0"
somewhere?  I have one customer that I set up using SSA drives with JFS2
filesystems and LTO1 drives and we average between 35 and 40MB/sec. and
some days as high as 45MB/sec (compression of data plays a large
factor).  Your Symetrix at 40GB/hr is only 11.11MB/sec!  BTW, this is
with no unusual tuning to the system, since this was more than enough
performance for their needs.  With a little more tuning I could easily
increase that by 50% and possibly double it if I really tried and that
is ancient SSA technology.  FC technology should be much faster.

I know there are many people who prefer raw lvs for there disk pools,
but on an AIX system I don't believe it is worth it.  I have never had
anyone show me raw lv numbers on AIX that I could not match (with far
less hassle) with a good JFS2 configuration.  If raw is the way you want
to go than I wish you luck.  However, if you are interested in switching
to using a JFS2 approach I would be glad to post to the list some simple
guidelines for configuring your environment to get much better
performance than you are reporting in your post.

--
Regards,
Mark D. Rodriguez
President MDR Consulting, Inc.

============================================================================
===
MDR Consulting
The very best in Technical Training and Consulting.
IBM Advanced Business Partner
SAIR Linux and GNU Authorized Center for Education
IBM Certified Advanced Technical Expert, CATE
AIX Support and Performance Tuning, RS6000 SP, TSM/ADSM and Linux
Red Hat Certified Engineer, RHCE
============================================================================
===


Hart, Charles wrote:

Thanks you for the link.. Good info!


-----Original Message-----
From: ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU]On Behalf Of
William F. Colwell
Sent: Friday, November 12, 2004 10:52 AM
To: ADSM-L AT VM.MARIST DOT EDU
Subject: Re: TSM and SATA Disk Pools


Charles,

See http://www.redbooks.ibm.com/abstracts/tips0458.html?Open

This was in a recent IBM redbooks newsletter.  It discusses SATA

performance

and to me it says that the tsm backup diskpool is not a good use for SATA.
Sequential volumes on SATA may be ok.

Hope this helps,

Bill
At 10:21 AM 11/12/2004, you wrote:

Been asking lots of questions lately.  ;-)


We recently have put our TSM Disk Backup Pools on Clarrion SATA.
     The TSM Server is being presented as 600GB SATA Chunks
     Our Aix Admin has put a Raw logical over two 600GB Chunks to create

a 1.2TB Raw Logical Volume

Right now we are seeing Tape migrations @ about 4GB in 6hrs, where before

on EMC Symetrix disk we saw 29-40GB per hour.  If anyone would like to share
their TSM SATA Diskpool layout and or tips we would much appreciate it!!!

TSM Env
AIX 5.2
TSM 5.2.4 (64bit)
p630 4x4
8x3592 FC Drives

Regards,

Charles

----------
Bill Colwell
C. S. Draper Lab
Cambridge Ma.