Comments on: What’s that ALUA exactly? http://www.yellow-bricks.com/2009/09/29/whats-that-alua-exactly/ Building blocks for virtualization... Tue, 16 Mar 2010 00:34:41 +0000 http://wordpress.org/?v=2.9.2 hourly 1 By: Duncan Epping http://www.yellow-bricks.com/2009/09/29/whats-that-alua-exactly/comment-page-1/#comment-4868 Duncan Epping Wed, 21 Oct 2009 18:34:17 +0000 http://www.yellow-bricks.com/?p=4053#comment-4868 Well an EVA is an asymmetric active/active. although you can access a LUN via both SPs, there's only 1 SP that owns the LUN. In other words there's a penalty for using the non-owner. Check Frank's excellent article on this topic: http://www.frankdenneman.nl/?p=5 Well an EVA is an asymmetric active/active. although you can access a LUN via both SPs, there’s only 1 SP that owns the LUN. In other words there’s a penalty for using the non-owner. Check Frank’s excellent article on this topic: http://www.frankdenneman.nl/?p=5

]]> By: mthibert http://www.yellow-bricks.com/2009/09/29/whats-that-alua-exactly/comment-page-1/#comment-4867 mthibert Wed, 21 Oct 2009 17:55:52 +0000 http://www.yellow-bricks.com/?p=4053#comment-4867 Fom what I understand you cannot have path thrashing with an active/active SAN like the EVA. You can only have path thrashing with an active/passive SAN like the IBM DS4000 with a policy path to FIXED. In the case of an active/passive like the IBM DS4000, the cache between the 2 SP (Storage Controller) is not synchronize like on a Netapp FAS3070. So, if you have 2 ESX host accessing the same LUN through a different SP, the ownership will flip between the SP. In some circonstance like high IO, the SP will not have the time to flush is cache before passing the ownership to the other SP. In the case of an active/active SAN like Netapp FAS and probably the EVA (Not an EVA expert) the cache are synchronize, so 2 ESX hosts can access the same LUN through different SP without having path thrashing, BUT since one ESX host will not use the prefered path the data will needed to go through the inter-connect cable between the SP(Netapp), so the SP owner of the LUN can write the data to the disk. I did a benchmark on the performance impact of using the a non-prefered SP and I saw a degradation of 20% in my environment. Fom what I understand you cannot have path thrashing with an active/active SAN like the EVA.
You can only have path thrashing with an active/passive SAN like the IBM DS4000 with a policy path to FIXED. In the case of an active/passive like the IBM DS4000, the cache between the 2 SP (Storage Controller) is not synchronize like on a Netapp FAS3070. So, if you have 2 ESX host accessing the same LUN through a different SP, the ownership will flip between the SP. In some circonstance like high IO, the SP will not have the time to flush is cache before passing the ownership to the other SP.
In the case of an active/active SAN like Netapp FAS and probably the EVA (Not an EVA expert) the cache are synchronize, so 2 ESX hosts can access the same LUN through different SP without having path thrashing, BUT since one ESX host will not use the prefered path the data will needed to go through the inter-connect cable between the SP(Netapp), so the SP owner of the LUN can write the data to the disk. I did a benchmark on the performance impact of using the a non-prefered SP and I saw a degradation of 20% in my environment.

]]> By: Tom http://www.yellow-bricks.com/2009/09/29/whats-that-alua-exactly/comment-page-1/#comment-4628 Tom Tue, 29 Sep 2009 15:35:12 +0000 http://www.yellow-bricks.com/?p=4053#comment-4628 Can anyone please comment on how ALUA is set up or enabled within an HP MSA 2012i SAN array?? Apparently this is now required because both HP and VMware will only support hardware iSCSI for this SAN. I have asked to HP but not yet received an answer. It's really not practical for us to get a new SAN, sigh, the iSCSI cards are expensive but cheaper than any other alternatives. Also, for the MSA 2012i, the SAN guide specifically says ALUA and MRU, I imagine this is the only supported configuration... Thank you, Tom Can anyone please comment on how ALUA is set up or enabled within an HP MSA 2012i SAN array??

Apparently this is now required because both HP and VMware will only support hardware iSCSI for this SAN.

I have asked to HP but not yet received an answer.

It’s really not practical for us to get a new SAN, sigh, the iSCSI cards are expensive but cheaper than any other alternatives.

Also, for the MSA 2012i, the SAN guide specifically says ALUA and MRU, I imagine this is the only supported configuration…

Thank you, Tom

]]> By: Chad Sakac http://www.yellow-bricks.com/2009/09/29/whats-that-alua-exactly/comment-page-1/#comment-4627 Chad Sakac Tue, 29 Sep 2009 14:56:36 +0000 http://www.yellow-bricks.com/?p=4053#comment-4627 The IOoperationsLimit value (default of 1000) isn't bad - and depending on your environment - can result in a very balanced config. As you increase LUN counts, and VM counts, it all averages out. It's only aggregated in the case (which is often what people test) - of a single datastore..... How long it takes for the command limit to be reached depends on a million parameters.... The IOoperationsLimit value (default of 1000) isn’t bad – and depending on your environment – can result in a very balanced config. As you increase LUN counts, and VM counts, it all averages out.

It’s only aggregated in the case (which is often what people test) – of a single datastore…..

How long it takes for the command limit to be reached depends on a million parameters….

]]> By: Kenneth van Ditmarsch http://www.yellow-bricks.com/2009/09/29/whats-that-alua-exactly/comment-page-1/#comment-4626 Kenneth van Ditmarsch Tue, 29 Sep 2009 14:15:02 +0000 http://www.yellow-bricks.com/?p=4053#comment-4626 Hi Duncan, Do you know how this was arranged in ESX3.5? I've tested RR in an ESX3.5 environment a while ago (HP EVA) and saw that both paths were loaded equally. Ex. without RR my IOPS were 1000 on the active HBA and with RR both HBA's did 500. I'm wondering how this "1000 commands-switch-over-policy" is working. (I know that the 1000-value is customizable.) Question obviously is, what's the average time it takes for the 1000 commands to be reached? If this would take for example 1 minute you would see 1 minute load on one HBA and one minute load on the second HBA, right? Hi Duncan,

Do you know how this was arranged in ESX3.5?
I’ve tested RR in an ESX3.5 environment a while ago (HP EVA) and saw that both paths were loaded equally.
Ex. without RR my IOPS were 1000 on the active HBA and with RR both HBA’s did 500.

I’m wondering how this “1000 commands-switch-over-policy” is working. (I know that the 1000-value is customizable.)

Question obviously is, what’s the average time it takes for the 1000 commands to be reached? If this would take for example 1 minute you would see 1 minute load on one HBA and one minute load on the second HBA, right?

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