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Looking for Input - Single vs Multi Site

cheazell
Advisor

Looking for Input - Single vs Multi Site

A quick description of our situation...

4 x ESXi 4.1 hosts with 4x 1Gb Nics (2 x onboard 2 x Card) dedicated to vSAN iscsi network.2 x ESXi and a dedicated iscsi switch are in one location and 2 x ESXi and a dedicated iscsi switch are in second location within the same building but on different floors. I have a truck of 4 x 1 GB uplink between the two iscsi switches. There is One P4000 VSA node per location.

 

My question is would a single site or multisite be the better design. Eitherway I'd use a single VIP. I'm just wondering if I can get better performance one way or another. I'd love your comments.

 

Chris

7 REPLIES
Paul Hutchings
Super Advisor

Re: Looking for Input - Single vs Multi Site

My understanding is that if you only have one node per location, and don't intend adding more, single site vs. multi-site shouldn't really be relevent because regardless of which node you lose, the other node has to have the data on it (assuming Network RAID10).

 

Once you get to 4 nodes upwards, multi-site (a floor in your case) would give you the ability to lose a floor but still keep running because the SAN will ensure that the data is striped to the appropriate node(s) across both sites to provide you with the right level of failover.

cheazell
Advisor

Re: Looking for Input - Single vs Multi Site

Thanks Paul,

 

Pretty well what I figured. My throughput just doesn't seem to be what I think it should be given the specs I outlined above. Still I'm going to see what 9.5 brings.

 

As a tangent - One thing I'm considering is moving the VSA to a dedicated host per site that will do nothing else. What VMWare license would you deem adequate? I'm thinking Essentials Plus to get their Bundle so that they can still be managed centrally via Vcenter. The only pause I have is the matrix of features show no Storage API for Array Integration or Multipathing. This may be moot though.

Paul Hutchings
Super Advisor

Re: Looking for Input - Single vs Multi Site

For testing throughput, if you've not already done so I'd keep it simple and connect everything to the same switch to start with, get the performance where you want it, then look at breaking the switches out - I'm no networking expert but it seems most iSCSI performance issues are related to poor switch configuration (assuming you follow all the best practise on the server/SAN NICs).

 

As for vSphere, I've not looked at many details for SAN/iQ 9.5 but is there going to be a multi-path plug-in for vSphere and if so does it offer a significant benefit over the native multi-path?

 

Difficult to say whether the VAAI is worth it or not, personally I always saw the VSA as being a cheaper route to getting a P4000 SAN on native hardware, and I can't help but thing that once you start adding up the costs of vSphere Std/Adv/Ent licenses the gap starts to close, haven't done the maths though.

Bart_Heungens
Honored Contributor

Re: Looking for Input - Single vs Multi Site

Hi all,

 

First, no there will be no multi-path plug-in in SAN/iQ 9.5...

You (still) have to follow the best practices from the document from HP... There is an updated version recently released which you can find here: http://h20195.www2.hp.com/V2/GetPDF.aspx/4AA3-6918ENW.pdf

 

Nice in ESXi 5.0 is that the binding process of the 2 VMkernels with the vmhba can be done in the GUI, in ESX 4 this had to be done via CLI...

 

Regarding VAAI yes I can assure you that you will get much better performance, this can be shown via a simpel test actually... Take a look at my blog blog.bitcon.be where I post often information regarding P4000... There are video's of HPstorageguy (he is great!) regarding VAAI, there is a list of all the new stuff of 9.5 and so much more...

 

And yes, I have vSphere 5.0 and 9.5 running in my test data center (where the blog is actually running on)...

 

Kr,
Bart 

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cheazell
Advisor

Re: Looking for Input - Single vs Multi Site

Hi Bart,

 

Thanks for the links I've check out the videos and the updated Docs. The question regarding VAAI that I have as a result is where the VSA sits in all of this. I understand if you are running a physical P4000 how you'll gain a benefit but when it is a virtual machine I'm not certain that you'll see that much.

 

I still think it would be better to move the VSA to a dedicated host that does nothing else but run the vsa but I don't really want to buy new vSphere enterprise licenses to do it the essentials plus bundle looks perfect from that perspective. I'm just not sure given the features matrix that essentials plus will offer enough to fully leverage the VSA.

 

Chris

Bart_Heungens
Honored Contributor

Re: Looking for Input - Single vs Multi Site

Hi,

 

The benefits of VAAI on the VSA's is indeed much lower since you are offloading to the ESX level of the server... Best performance is in that case the P4x00 physical boxes...

If you want a dedicated ESXi server for the VSA, then the free ESXi as such is already enough I assume... In my case I have VSA's running on the same server as my VM's... HP recommends that the VSA's have 2GHz of CPU and 1 to 4 GB of memory assigned... All therest can be used for other VM's...

 

Kr,

Bart

--------------------------------------------------------------------------------
If my post was useful, clik on my KUDOS! "White Star" !
My blog: http://blog.bitcon.be
cheazell
Advisor

Re: Looking for Input - Single vs Multi Site

A follow up question...

In my setup I currently have a Stretched Single Site Cluster comprising of 2 nodes (1 in each location) plus a FOM in a 3rd location. I have 2 dedicated iscsi Switches (2910al) again 1 per location. I have 2 Hosts in each location for a total of 4 (not counting the FOM). The switches have a static trunk between them. Each host has 2 dedicated nics connect to location A and 2 to location B. I've done this to try to build some resiliancy into the design but I'm second guessing myself.

 

Would it be better to have Servers at Location A go into the Switch at Location A exclusively and B into B and allow the Trunk to do its work for the Network Mirror aspect?

 

Chris