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How to view I/O down the various paths to disks?

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Kenneth Ray_5
Occasional Contributor

How to view I/O down the various paths to disks?

I've heard that on Tru64 5.1 that the I/O is balanced down all paths to the disks. How can I verify that...I would like to be able to view the I/O down the paths. How can I do this?

Thanks,
8 REPLIES

Re: How to view I/O down the various paths to disks?

There's a nice little utility calle "monitor" that shows IO. It should be on the open source cdrom.

Mario
Kenneth Ray_5
Occasional Contributor

Re: How to view I/O down the various paths to disks?

Well, it show's I/O, but it shows I/O for the disk and not the individual paths to the disk so I can verify that Tru64 is balancing I/O down all paths. Am I making sense?

Thanks,

Re: How to view I/O down the various paths to disks?

I'm not aware of anything in Tru64 that will give you this detail. We've done failover testing by removing paths by pulling the connector.

I would imagine that what you're looking from should be available from the SAN's point of view.

Mario
Kenneth Ray_5
Occasional Contributor

Re: How to view I/O down the various paths to disks?

I was afraid that was going to be the case. It sure would be nice to be able to do a view from the host side to see the balance of I/O down the various paths.

Thanks,
Mark Poeschl_2
Honored Contributor

Re: How to view I/O down the various paths to disks?

For the Brocade switches at least there are really easy-to-use performance monitoring tools that are available right on the switch management GUI. Just watch the ports connected to your server and see if the loads are relatively similar. Admittedly you won't be able to isolate loads to specific storage volumes, but if all the server's HBAs are equally busy, I'm not sure you care.
Kenneth Ray_5
Occasional Contributor

Re: How to view I/O down the various paths to disks?

Yeah, that's exactly what I am doing now. Utilizing brocades perf. monitor java applet.

thanks,
Johan Brusche
Honored Contributor

Re: How to view I/O down the various paths to disks?


Ken,

"hwmgr get attribute -category disk", will show you all the paths and the associated IO.

__ Johan.


_JB_
Hein van den Heuvel
Honored Contributor
Solution

Re: How to view I/O down the various paths to disks?

Kenneth,

Of course you can monitor that!
Use hwmgr like Johan mentions and you will see 'wds' entries for each bus. Those are 64 bytes each.

A single shot will give you an indication of the balance since boot.

I'll attach a script with sample output that you can run before and after a test to gather the counters at that time. Then run the script once more to evalutate the results.

Note though that Tru64 does NOT balance just for the heck of it. It only balances if that is deemed useful. It will first attempt to issue the IO on a 'local' adapter. If that is not available, or too busy then it will look for a 'NEAR' adapter to use. (important in a GS1280. In a GS320 all remote QBBs have effectively the same distance.)
So if you run from one processor, and just do read after read, you'll see just once channel being used.... and that's just fine.

hth,
Hein.