Originally posted by: emreb

Hii all
We connected the aix to the ibm ds4700 storage via fiber.
Now We need 500 gb disk space what do you suggest to me ?
There is 10 300gb 15k disk in a volume so

1.could I create small luns on storage then aggreate in aix volume groups ?if so how much size I can allocate for each size ?

2.Or could I create 500g single lun and define in single volume group ? if I create single lun what queue depth I have to define for that single disk for max performans ?queuedepth=number of disk*queue depthsize for each disk ?
or I must set queue depth in these situations ?

Best REGARDS..
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Originally posted by: cggibbo

Generally speaking AIX performs better with a larger number of small luns versus a single large lun. But it really depends on what you need in terms of performance.
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Originally posted by: Sumanth.Sharma

I would like to disagree.

The I/O performance is determined by the ability of the Storage Array, the efficiency of the SAN fabric and the speed and quality of the HBA driver.
On the AIX front the Native MPIO driver/ or any other Multipathing software only lets you choose the active path(s) and load balancing features.

Since you need 500gb capacity, you may want to have say 5 100GB luns and add it to a Volume manager locally, however the size of a single lun may not be significant since you would be exposing them as logical volumes to the application right ?

The one AIX thing here is that, say with a strorage processor/controller with 512 queues and a LUN with Queue depth of 32 would mean that on the Target initiator or HBA, 1 HBA can suuport IO for upto 512/32 = 16 LUN i/o on single hba beyond which QFULL error will occur.

Typically this QFULL is gracefully handled but If am correct in Aix typically after the 3rd QFULL error, it is treated as an I/O error.

Since you need 500gb, even if you have 1LUN size as 32GB , if you have 2 HBA on the machine you can safely present 32LUNS (32GB) upto 1024GB i.e 1TB to that host so even with a ypical combination you would be fine.

Am not an expert on the Storage array front so you would be well advised to look at the performance graphs of your Array (ds4700) in your product documentation and follow the recommendations.

But apart from the QFULL error caveat (i.e. after 3 QFULL errors Aix treats as I/O error) the actual effective I/O performance is determined by your Array and SAN fabric.
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Originally posted by: Sumanth.Sharma

Correction in my 2nd line, its not speed and quality of HBA driver rather it is HBA adapter.

PS: Emulex and QLogic have 10gps HBA's as well. Choose them based on OS Support, Emulex has better OS support, QLogic is yet to support many latest OS distributions like SLES-11 etc.
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