Assigning XSAN MDC to a RAID controller

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Assigning XSAN MDC to a RAID controller

In reading the XSan administration guide, it specifies that you should assign data LUNS to each controller for balance. So LUN 1 goes to controller (A) LUN 2 goes to controller (B) LUN 3 Goes to controller (A) LUN 4 goes to contoller (B)

I am looking at my current set up that was installed by an integrator and all of the Data LUNS are assigned to one controller (A) and the MetaData LUN is assigned to LUN (B). I also noticed that Force Read Ahead is disabled on both controllers.

I am having some performance issues and plan on running a file system correct when I can take the XSan offline. Since I will be taking it down, and these settings appear incorrect... I was wondering if I should change the Controller assignments for the LUNS and enable Forced Read Ahead?

Any thoughts?

Thanks,

Ray

Xserve, Mac OS X (10.6.6)

Posted on Dec 8, 2014 7:34 AM

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Answer 1

Dec 8, 2014 6:32 PM in response to RayfromMD

The VTrak config scripts in Apple's KB all have LUNs divided evenly between controllers. See the scripts in articles linked from Promise VTrak: Configuring for optimal performance. I'm not sure if the x30 VTrak built in scripts do the same thing.

Re Forced Read Ahead see this guidance in http://kb.promise.com/Attachment378.aspx:

• Controller Settings, Forced Read Ahead: Enable or Disable (aggressive pre-fetch)

o Controller Forced Read Ahead should be enabled for large block sequential access such as rich

media type applications

o Controller Forced Read Ahead should be disabled for Random IO type applications

You should test with each enabled to see which works better for you.

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Answer 2

RayfromMD Author

Level 1

5 points

Dec 15, 2014 11:17 AM in response to Claudio Sanchez1

Hi Claudio,

I appreciate the input. I think I will follow Promises method and divide the LUNs evenly. I don't see any compelling reason to assign all the DATA LUNs to one controller and the MetaData to the other... actually it seems that would slow things down.

Thanks,

Ray

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