3PAR host port interrupt coalescing

[Tim_Chilton]

I am curious as to the proper interrupt coalesce setting for host facing ports.  I've seen various thing on the web that indicate that it should be set to enabled for RCFC ports, but have found nothing indicating a reason that it should be moved from the IMC default of disabled.  Could someone point me in the right direction?

[Ashoka_R]

3PAR uses interrupt coalescing at the controller host HBA to reduce CPU load in a multitenant environment so if you only have a single threaded app or you only have very low queue depth,  you'll see higher latencies. For write coalescing, the reason is the HBA will hold these I/O's until it's buffer fills before sending a interrupt to the controller CPU to process the I/O so you incur a wait state.

If you really do have a single threaded app then turn off "intcoal" on the HBA port and it will issue a interrupt for every IO posted, you will also probably want to adjust the host HBA queue depth also.

[PawelA]

Could you please explain if it is recommended to use it on RCFC ports?

I am curous which will have better result on write latencies when replicating synchronously.

Regards,

p.a.

[yapkl]

Have a look at the 3PAR Remote Copy User Guide ->

http://h20565.www2.hpe.com/hpsc/doc/public/display?docId=emr_na-c03618143

General System Restrictions

• For more information about HPE 3PAR OS support levels, see the HPE 3PAR Operating System Upgrade Pre-Planning Guide, available at the following website: Hewlett Packard Enterprise Storage Information Library (http://www.hpe.com/info/storage/docs)

• Interrupt coalescing must be disabled on the RCFC ports.