SSA Performance ! How to improve

[polani]

Dears,
We have two p6300 Servers attached to one SSA Subsystem using one SSA RAID Controller each.
There is one single loop and one SSA RAID array ( RAID-5) which is around 450GB. SSA disks are 10 K RPM with 72 GB capacity each.

Now the problem is that when i run a single copy command on SSA raid array to copy data from one filesystem on SSA to another fs on same ssa then i am able to get only speed of 3.7 MB/sec
!!!!!!!!!!!!!!!

and when i do the same copy command to copy the data from SSA to one
of the internal disk ... it give me a speed of 6.3

MB/Sec.............!!!!!!!!!!!!!!!!!!!!!!AHHHHHHHH
SSA claims up to 40MB or 80 MB/Sec....can any body tell me where that
calimed performance gone
!!!!

what i have configured wrong
There is no FAST write cache available....what i should do to improve the performance
......

Are there any parameters can be changed on SSA level ....Advices
appreciated and thanks in advance



Polani


Here comes polani Once again!!!

P690 Certified Specailist
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[MoshiachNow]

HI,

Please post the result of :

lsattr -El sys0

Thanks

Long live king Moshiach !

http://www.7for70.com/

 

[RodKnowlton]

What sort of speed do you get copying to /dev/null from the SSA?



Rod Knowlton
IBM Certified Advanced Technical Expert pSeries and AIX 5L
CompTIA Linux+
CompTIA Security+

 

[polani]

Thanks dears for your prompt responses!!!

Infact Rod's question is more focusing towards read performance of that SSA RAID... i did not do that however copying of SSA to an internal disk of the system is done and the results are :

When we are copying the same 2184 MB data from SSA file system to another filesystem on internal disk it is taking 5 minutes 48 seconds. (6.2MB/sec)

Now what's gone wrong here.... There is infact no fast write cacahe there .... however from SSA cabling point of view , is there any suggestion you can give to me.

If i delete existing single RAID-5 Array and create two small size arrays ( 3+P) on same loop do you think about any performance improvement?????

Or if i brought in two SSA cards ( one into each server ) and then create another loop and then one small RAID array onto it ( 3+P) will there any performance improvement expected?????

I really appreciate your expert opinions



Here comes polani Once again!!!

P690 Certified Specailist
HACMP & AIX Certified Specailist
AIX & HACCMP Instructor

 

[DukeSSD]

I would think that less disks would equal less heads to read / write so the performance would be less.
Just a guess though.

 

[DukeSSD]

Have a flick through:

http://www.redbooks.ibm.com/redbooks/pdfs/sg245750.pdf

and:
ftp://ftp.software.ibm.com/storage/7133/pdfs/ssaplan.pdf
Chapter 3 of the second book is all about performance.

Make sure the adapter, enclosure and disk firmware and the aix filesets are all up to date:

http://www-1.ibm.com/support/search.wss?rs=505&tc=STCXNXH&q=ssg*&sort=desc&dc=D400&dtm

 

[polani]

Thanks dears!

For ur reply... I have seen that book especially SSA planning guide and refernced chapter.

All it says that FW cache improves the situation however beside FW cacahe there is no prominent suggestions or advices.....

I want to invite u all guys to have a word about IBM claimed SSA performance of 20-30 MB/s ...
Have any one of u achieved that ???

or what speed u are gaining from ur SSA subsystems



Here comes polani Once again!!!

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[RMGBELGIUM]

We are getting read speeds of 16 Mb and write speeds of 10 Mb, this was tested through the "dd" command, writing 32760 blocks of 32 k.

greetz

R.