SecurePath Load balancing work with ASM/RAW disks?

[Hanry Zhou]

we have 4 HBA'S, and Round Robin policy is configured on securepath. We only provide one of 4 devices files to ASM disk group.

My question is, is load balancing working across all 4 devices, although only one of them being used in ASM group?

If yes. why we have seen high i/o %busy rate on the disk provided to ASM, and low rate on the other 3 devices?

Please advice.

Thanks!

[Steven E. Protter]

Shalom,

ASM is a total control option and all i/o is managed by Oracle. The load balancing if set up to balance across all four disks round robin will do just that.

Oracle ASM is not very respectful of the OS and acts as if it owns the whole system. ASM is making more demand for i/o and will do so based on database transactions.

I don't see this as a load balancing issue.

SEP

[Duncan Edmonstone]

Which secure path product are you talking about here? Secure Path for Active/Passive or Secure Path for Active/Active?

I'm Assuming by the fact you mention you see 4 devices you mean Secure Path for Active/Active?

In this case for "raw" applications like Oracle ASM, you should be using the virtual devices created under /hpap rather than the normal devices in /dev/rdsk

Also depending on the disk array and workload profile, Secure Path won't necessarily send an equal amount of IO to each path - what sort of disk array do you have?

HTH

Duncan

[Hanry Zhou]

we are using SP Active/Active with XP12K.
The fact that we only provide AMS disk group one device files out of total of 4, coult that cause the problem? If it is, then the load balancing could not really across all 4 devices. the device is being used in ASM has significat large i/o %busy rate then any other 3 devices, and so to avserv.

Is this because we have not use the virtual device suggested by Dun, and how to create such virtual device, and how to create the connection betweeh this virtual device to all 4 real devices?

Thanks,

[Duncan Edmonstone]

Hanry,

There's a chance that the numbers simply don't look right because the kernel counters that sar reads simpoly aren't updated corerctly when Secure Path is in the equation, so I really don't know there.

The virtual devices should already be there - just run "autopath display" and you should see them listed for each LUN on the XP.

HTH

Duncan

[Hanry Zhou]

What confuses me about is what device file I really should provide to DBA.

We have provided one of common device file to DBA, and he will use it to add into disk group. this common device is one of 4 devices files, and shared by all nodes in the Oracle RAC cluster. this is how we have done here. However, now, I doubt if this process really take advantage of load balacing as supported by SecurePath. Once only one device file is provided to ASM, then ASM seems only use this one to read/write, and the metrics shown by sar -d seems supporting this theory. I can understand all 4 deivces will be configured into lvm, and we can therefore ensure the load balance, however, since we only use raw devices, so lvm is no in play here.

I am kind of believe that ASM doesn't really use load balancing by securepath, but what is the way in ASM to support load balancing?

If anybody please help me out.

[Hanry Zhou]

Yes. virtual devices were already created and could be shown by autopath display. However, can I provide this to ASM disk group? Regardless, the virtual devices are not identical across all 4 nodes cluster, since they all have to be shared, that would be impossible to add them in the disk group, if they are not identical.

[Hanry Zhou]

Can anybody please take a look at this thread? I have really been bothered by this question.

[Alzhy]

Yo! Hanry,

So did you end up using Autopath's Virtual Device /hpap/* which should do Load Balancing for you to your XP12000?

We're thinkning about moving to AutoPath as well. Our current ASM config use VxVM Raw devices that are carved 1 Vol per 1 XP Disk -- this simply use VxVM's DMP.