9 Replies Latest reply: Oct 6, 2011 3:03 PM by Avi RSS

ALUA on CX3-80

Fredster

Hi guys,

 

I have a question about ALUA on my CX3-80 (Running FLARE 26)

 

I guess I understand the basics of ALUA:

 

1) Set LUN to FAILOVER MODE 4

2) As long as the LUN gets accessed over the owning SP I have optimized access

3) When the LUN gets accessed over the non-owning SP I have non-optimized access

 

So, I can now reach my LUN via the active AND the inactive service processor. Any traffic that is directed to the non-active service processor will be routed internally to the active service processor.

 

What I am not sure about is the following:

 

What advantages does this give me?!?

 

  • I guess tresspasses don't matter all that much anymore, but are there any other advantages?
  • Are there any disadvantages?
  • Is there a chance the host will do I/O the non-optimized paths, whilst the LUN is fully reachable by the optimized paths, or will it always prefer the optimized paths?
  • Using PowerPath 5.5.0, will ALL paths get used at the same time (optimized+non optimized) allowing greater bandwidth?
  • Can I use this in Windows without problems?
  • Can I use this in VMWare without problems?
  • Any other Gotcha's?

 

I hope some people here have experience with the ALUA feature and can offer me some insight

 

Thanks in advance for any answers!

 

Fred

  • 1. Re: ALUA on CX3-80
    glen

    When using ALUA, the principal benefit is that it cuts down on trespassing. If you lose access to LUN on main path, IO is accessed over the internal pass thru. If the path comes back, you save the time you would have spend in trespassing the LUN.

     

    The non-optimized path is not normally used by PowerPath in normal operation.

     

    I believe that only Windows 2008 is supported with ALUA.

     

    ESX 4.x is supported with ALUA, but not earlier.

     

    See Support Solution emc254967 for the Agent information and emc245445 for iSCSI

     

    glen

  • 2. Re: ALUA on CX3-80
    Christopher Imes

    Simply wanted to also point you to a short whitepaper that describes the feature and its benefits which is entitled:

     

    White Paper: EMC CLARiiON Asymmetric Active/Active Feature — A Detailed Review

     

     

    It is available from PowerLink via the following breadcrumb trail:

     

    Home > Support > Technical Documentation and Advisories > Hardware/Platforms Documentation > CLARiiON CX3 UltraScale Series Systems > CLARiiON CX3-80 > White Papers

     

    Furthermore, there is a matrix which lists the supported configuration using either native MPIO where for Windows your choices are limited to Windows 2008 as mentioned already or, as you'll notice, your support broadens when using a supported version of PowerPath.

     

    alua.jpg

     

    One other reason to enable it might be to support certain features such as vSphere VAAI (vStorage API for Array Integration) which provides hardware acceleration (offload to the array) for various primitives and was introduced in vSphere 4.1.  Please note, however, this is not relevant for your environment as it also requires array support, as you would expect, which is currently only available in FLARE 30 in addition to having ALUA enabled for your registered ESX hosts.

  • 3. Re: ALUA on CX3-80
    SKT

    is this chart relevant to flare 26? I am under the impression that ALUA is supported from only release 28.

  • 4. Re: ALUA on CX3-80
    Avi

    ALUA is supported since Release 26 of FLARE.

  • 5. Re: ALUA on CX3-80
    glen

    Please remember to mark the question as Answered when you get the correct or best answer. Also, please award points to the person providing the best answer.

     

    glen

  • 6. Re: ALUA on CX3-80
    giograves

    Actually, while ALUA FLARE support did begin in 26, VMware supports ALUA only with SCSI-3 reservations, which is not available to the CX3 (SCSI-2 reservation in flare code 26).

  • 7. Re: ALUA on CX3-80
    glen

    Most of these issues have been fixed in updates - see Support Solution emc227055  and emc106122 for more information.

     

    glen

  • 8. Re: ALUA on CX3-80
    SKT

    How did this implementation work for?

  • 9. Re: ALUA on CX3-80
    Avi

    SKT - what information are you looking for? Implementation details can be found in the ALUA whitepaper on Powerlink.