Shared SAS for HA; will this work?

[grogthegreat]

Sorry if this has been answered before but I tried searching on here and google!

So the initial goal is to get two ESXi hosts running off of a single shared pool of storage for as cheap as possible with great performance. I currently have a 36 bay Supermicro 837E16-RJBOD1 which has a built in 6Gb SAS expander.

The question:
Could I take two Dell ESXi servers and put a LSI 9285CV-8e raid card in each server and then connect both raid cards to a LSI SAS switch (LSI6160) and then connect the Supermicro case to the SAS switch as well? The switch would be configured so that both raid cards would see the same set (say 6) hard drives. I would have one raid card set the 6 drives into a raid array and then import the foreign configuration in the other raid card. Both servers would in theory see the same virtual drive on which I could put the VMware VMFS cluster file system which should prevent any issues with more than one server access the same virtual drive at the same time.
So would this work? In practice I know I'd want two SAS switches and the appropriate cabling for redundancy. I'd also get CacheCade Pro 2.0 on both raid cards and each raid card would need it's own group of SSDs as I know they couldn't share that.

In this setup I image that performance would be very very good and the cost is a lot lower than a iSCSI setup. Other than the obvious SAS cable length limitation, am I missing something here?

Thanks in advance!

 

[grogthegreat]

Sorry for bumping my own thread. Should I move this to the storage subforum?
From my reading, I've seen several setups like the one described above but they always reference HBAs and not raid cards. I know that technically raid cards can considered a type of HBA but finding no references to raid cards in this type of shared SAS storage is why I'm concerned. Would the two raid cards interfere with each other?
Here is a picture of the possible setup in case my description above wasn't clear.

 

[D-EJ915]

As far as I can tell it won't work like that. It doesn't matter what the filesystem is because the controllers are both doing block-level access to the arrays.

 

[lopoetve]

Sure. It'll work fine, but not in that config. Shared SAS is fine, if your array is on the HCL. Now, just having a Supermicro with an expander - that won't share, as it's a JBOD and not an array, but if you have an actual array with controllers, then it'd work.

 

[grogthegreat]

Thanks for the replies!
I also just discovered this wouldn't work ---- for now.

lopoetve: I don't want to use an enclosure that has built in raid as I don't think it would support CacheCade Pro 2.0 which really helps for VMs. Plus they are way more money for simply including a raid card.

Before I was searching for "shared SAS" but it turns that LSI and I think alike only they are calling it "HA-DAS" or high availability direct attached storage. The main problem is that it won't be out till 4th quarter of this year.

This link shows it working with two LSI 9265-8i cards which implies that it will work with 9285-8e cards as well and only a firmware change is needed: http://www.lsi.com/downloads/Public/Direct Assets/LSI/HighAvailability_TechBrief_091311.pdf

My main concern at this point is that they are only mentioning it working with Microsoft Server 2012. I think it would be a huge shame if it wasn't available to work with VMware, or even worse, only available with the purchase of a cluster-in-a-box system from an overpriced vendor with only Server 2012 on it.

Here is the tech brief that is rather light on details: http://www.lsi.com/downloads/Public/HA-DAS/docs/LSI_TB_HighAvailabilitySolutions.pdf

The fact that compatibility with CacheCade or with the LSI 6160 sas switches is not mentioned at all is slightly concerning. If both of those worked, I'd think it would be a rather huge marketing point that they would want to mention. If it does work with VMware, CacheCade, and the sas switch, this HA-DAS solution might be far faster, easier, and cheaper than any fiber or iSCSI SAS solution with the only downside being you are limited to 25 meter cable lengths for the active sas cables.

So it looks like my plan won't work now but might work in 6 months depending on how LSI releases this. Ideally it will just be a free firmware update that it OS independent but that is probably too optimistic.

 

[geiger]

It looks like a hardware based implementation of storage spaces.

 

[lopoetve]

Thanks for the replies!
I also just discovered this wouldn't work ---- for now.

lopoetve: I don't want to use an enclosure that has built in raid as I don't think it would support CacheCade Pro 2.0 which really helps for VMs. Plus they are way more money for simply including a raid card.
.

It's WAY more than just a RAID card There's failover capacity built in, lun presentation and management, etc - it's a full array.

 

[grogthegreat]

It's WAY more than just a RAID card There's failover capacity built in, lun presentation and management, etc - it's a full array.

I see your point. Failover is important and at this time it is the only way for a pure SAS solution to present a lun to more than one server. Still the cost increase over a normal JBOD SAS2 expander chassis is a bit much in my opinion.

However once HA-DAS is out it will have both of those plus (hopefully) cachecade and be way less money. Much better performance for significantly less money is obviously very tempting although the wait and the current lack of compatibility info is annoying. I did send a message to LSI asking some questions so hopefully they will answer one or two. If so, I'll share the info here. Otherwise I'll be waiting with everyone else. If I was able to wait for the Chenbro CK23601 card than I can wait 4-5 months for this!