topic Re: VA7100 Config in Disk Enclosures

VA7100 Config

Joseph C. Denman — Wed, 20 Nov 2002 19:06:43 GMT

Need a little info.

Got a va7100. Will it help performance to stripe vg's across the 2 controllers? I was planning on creating 2 luns and striping the vgs. Does anyone have any good information on initial configuration?

Thanks,

...jcd...

Re: VA7100 Config

Ted Ellis_2 — Wed, 20 Nov 2002 19:18:03 GMT

if you are going to create 2 LUNs and then add them to a single volume group, then you can achieve load balanceing (performance improvements) by making the primary path of LUN1 controller A and the other LUN controller B. Then the I/O to each LUN will flow across separate controllers.... Is that what you were asking?

Ted

Re: VA7100 Config

Jeff Schussele — Wed, 20 Nov 2002 19:28:45 GMT

Hi Joseph,

Yes you'll get a performance increase, but I would caution you to also consider redundancy.
Do you have a plan to mirror the VG's LVs through separate controllers?
In your proposed layout if you lose one of the controllers or it's link - you'll lose that VG.

Rgds,
Jeff

Re: VA7100 Config

MANOJ SRIVASTAVA — Wed, 20 Nov 2002 19:48:02 GMT

Hi Jcd

Ideally to achive redundancy and load balacing you need to have atleast two contorllers visilbe tot he disk that form the vg and the vg created with altreante diska s primary and secondary . it is better not to ahve bulky vg's and we use aa maximun of 4 disks or like 32 Gb per vg . Also the best perfomance achived is if the lvol is striped acroos these disks and hte block size as required . we use Oracle so gernally that is 8K .

Manoj Srivastava

Re: VA7100 Config

Eugeny Brychkov — Wed, 20 Nov 2002 21:59:55 GMT

Joseph,
I'm in doubt that you will have great perfomance increase (but not perfomance loss)... if you would have VA7400 then yes. But VA7100 has only one Redundancy Group (RG1) and perfomance path for all LUNs created within VA7100 is Controller 1 (C1). Another controller C2 should be used for redundancy. It is because of internal VA7100 architecture. See http://forums.itrc.hp.com/cm/QuestionAnswer/1,,0x59525c7609e9d61190050090279cd0f9,00.html and http://forums.itrc.hp.com/cm/QuestionAnswer/1,,0x521006350fe2d61190050090279cd0f9,00.html . So I would create one big LUN with primary path through C1 instead of two ones. Anyway LUN's data will be protected by VA's hw and fw (RAIDs, checksums etc) very well
Eugeny

Re: VA7100 Config

Vincent Farrugia — Thu, 21 Nov 2002 10:25:20 GMT

Hello,

Usually, 2 controllers are meant for redundancy, not for performance increase. I.e., if one controller fails, you would still have access to the LUN through the other controller.

If you want BOTH, there is a way; through VxVM. VxVM offers dynamic multi-pathing (DMP), with which you setup your LUN with redundancy in the same way as before, but it access the LUN through both controllers at the same time.

You need a licence of VxVM to do this. Base VxVM (free with HP-UX 11i) does NOT offer this capability.

HTH,
Vince

Re: VA7100 Config

Insu Kim — Thu, 21 Nov 2002 12:24:35 GMT

You need to think about "performance path".
The performance path is the most direct path that the host can take to the data in the array.

The performance path is always faster path in terms of data transfer rate.
In the VA7100, the performance path is always specified by the device file for controller 1.
Since the VA7100 has only one redundancy group and the secondary controller is used only for failover.

That is, the primary controller is always the most direct path to the data.
If controller 1 fails, the host will use the secondary path to controller 2.

In the VA7100, if data access through the secondary controller attempts, there's a performance penalty associated with that operation.

After all, it doesn't look good to stripe LUNs across both controllers for optimal performance in the VA7100.

Hope this helps you

Re: VA7100 Config

Joseph C. Denman — Thu, 21 Nov 2002 14:56:57 GMT

Thanks. I had read somewhere about needing to use the performance patch on the 7100. You folk confirmed it. Thanks again.

...jcd...