StoreVirtual Storage
cancel
Showing results for 
Search instead for 
Did you mean: 

VSA - How does Virtual RAID work?

Paul Hutchings
Super Advisor

VSA - How does Virtual RAID work?

I'm looking at how I could do a really low cost remote replication to a VSA.

 

For our main cluster, our FOM sits on vSphere on a HP Microserver which is in a third location with gig ethernet into the iSCSI LAN.

 

Right now I'm thinking I could drop a couple of cheap SATA drives into that Microserver and run a VSA on it (we have the licenses spare).

 

Where I'm not so clear is that the physical P4000's run physical hardware RAID.  In the documentation for the VSA it refers to "Rirtual RAID" but I'm not clear if this offers any redundancy?

 

Basically what happens if you have 4 VMDK's allocated to your VSA and one of the VMDK's disappers to to a failed drive etc.

 

Thanks,

Paul

11 REPLIES
Bart_Heungens
Honored Contributor

Re: VSA - How does Virtual RAID work?

Hi,

 

In the physical boxes of the P4000 series there are 2 levels of RAID implemented... Hardware RAID5 on harddisk level to avoid data loss in case of a hard disk failure, and also network RAID accross the (minimum) 2 storage nodes... This to avoid that data is lost in case of network outages or storage node losses...

 

With the virtual version VSA, the hardware RAID level is implemented by the disks where the VMFS volume is located and where you will store the VMDK files attached to the VSA...

 

You do not mention which P4000 solution you have but know that, in case of the P4300 or P4500 with SAS drives, performance will go down when you add a third VSA with SATA drives... The network RAID will spread all data accross all nodes which means that 33% of all data is hosted on 'slow' SATA disks...

 

Kr,

Bart

--------------------------------------------------------------------------------
If my post was useful, clik on my KUDOS! "White Star" !
lando_uk
Advisor

Re: VSA - How does Virtual RAID work?

If you're going to setup a VSA on the microserver, use a single dedicated disk for each VSA, that way you can run Network Raid 10 on them and be redundant without having to use any hardware raid on the server.  If you share the VSA's across SATA disks, it'll run horrible.

Paul Hutchings
Super Advisor

Re: VSA - How does Virtual RAID work?

Thanks both.

 

Just to clarify, I wouldn't be planning on adding the VSA's to our existing P4000 clusters (we have a P4500 15k SAS and a P4300 MDL).

 

My thinking was simply that 2tb SATA drives are dirt cheap so why not use one of those VSA licenses to setup a standalone VSA and use it as a remote copy target so I have a replica of our main vSphere volumes on a physically separate system, kind of as a very last resort for DR.

RonsDavis
Frequent Advisor

Re: VSA - How does Virtual RAID work?

Virtual Raid spans the data across whatever LUNs you provide it. It will mostly fill the first disk, then mostly fill the second disk, and so on. 

If you want any redundancy on the local node, it has to be done with hardware raid. Also, if you want the best performance, in most cases you will want to carve LUNs out of a larger pool of disks, otherwise all of your I/O will hit just a subset of the disks. 

 

Paul Hutchings
Super Advisor

Re: VSA - How does Virtual RAID work?

Thanks Ron.  Performance really isn't an issue here.

 

It is literally a case of having a Microserver which does nothing but sit in a third physical site running the FOM VM, having a pile of VSA licenses doing nothing (yet), and thinking "Could I just chuck a $50 drive in the Microserver and run a VSA as a remote copy target?".

 

That way I have a lot of redundancy as in multi-site SAN with snapshots, regular backups, plus a third DR SAN.

 

I don't see whether the CPU reservation for the P4000 VSA is mandatory or not though?  I seem to remember having to remove all the reservations on the FOM VSA to allow it to boot, but it boots and runs just fine.

 

I'm a little unclear (reading the docs now) whether I'd need to create a new set of snapshots on my current P4000 clusters for the volumes I want to remote copy?  I already take snapshots at X hour intervals of those volumes.

 

Also I don't really care if the DR microserver fails as it's not production and it's a self-contained P4000 Management Group so if it goes up in smoke because a drive fails I just delete the remote snapshot settings in the main P4000 Management Group and rebuild the Microserver and start again... don't I?

 

Basically unless I'm missing something, for $100 in parts it seems I'm be crazy not to do it?

RonsDavis
Frequent Advisor

Re: VSA - How does Virtual RAID work?

If you try and reserve a full CPU for the VSA it won't always boot, because ESX(i) doesn't always feel it has that much CPU to give out. Frankly if you aren't running any other VMs on the host besides the VSA, setting a reservation doesn't matter anyway.
If support asks you to put the reservation back on, humor them and turn it on again, but don't try for a full cpu, just use the 2000 they ask for, unless your CPU is less than 2ghz.
Steve Burkett
Valued Contributor

Re: VSA - How does Virtual RAID work?

The current HP ProLiant Microserver only has a 1.5Ghz proc! :)  Great little box though.

 

Paul, did you ever get this set up?

 

Paul Hutchings
Super Advisor

Re: VSA - How does Virtual RAID work?


Steve Burkett wrote:

The current HP ProLiant Microserver only has a 1.5Ghz proc! :)  Great little box though.

 

Paul, did you ever get this set up?

 


Yeah the CPU speed was my biggest concern.

 

Right now the (rough) plan is to get a box at the start of next year, probably an ML150 or ML330 and to chuck a few large SATA or MDL drives in it and enoug RAM to use it as a new FOM host and to host one or more VSA's where speed isn't critical.

 

Of course the nice thing with the Microserver is that it draws next to no power so we don't need too beefy a UPS in that closet.

 

Shame the VSA's don't seem to be configurable with more CPU and NICs.

JordiVidal
Occasional Visitor

Re: VSA - How does Virtual RAID work?

if I need to implement a fisical RAID on each node?

 

Example:

 

I want to Use VSA with Adaptive Optimization and I have 2 nodes and on each node:

 

5 x 1,2 Tb SAS 6G

2 x 200 Gb SSD 12G

 

I can simply make a pool of this discs and implement a NRAID 10?

 

or I need to implement a RAID 5 with the 5 SAS discs and RAID10 with 2 SSD discs,  and above of all this, implement the NRAID 10?

 

Thanks to all!

 

Jordi Vidal

oikjn
Honored Contributor

Re: VSA - How does Virtual RAID work?

Just to reiterate what bart said. 

 

The VSA drives are implemented as Raid0 Stripes, so if you want hardware redundancy at the VSA level you need to provide that before the VSA (you can present hardware raid LUNs direct to the VSA or you can present a vhd that is protected by raid below it).

 

beyond that, the VSA and hardware nodes act and program the same way, but keep in mind that performance is only as good as the underlying hardware.

 

The other item of concern I see with your comments is that I"m not 100% sure if you are thinking you are going to do snapshots or are thinking you are going to create a multi-site cluster with this setup.  STAY AWAY from multi-site with what you mentioned here.  Keep in mind that with true synchronous replication all your data is going to be as fast as the SLOWEST node, so if you put on one or two slow VSAs on the remote site, it will bring your local performance to its knees!  YOu will have latency/throughput and then Node performance all to worry about.  I would highly suggest sticking to remote snapshot replication for DR or if you require a true multi-site san, you have to pay the price and buy the true matching nodes for the cluster.  Any cheaper and you are going to have problems. 

 

 

oikjn
Honored Contributor

Re: VSA - How does Virtual RAID work?

and to your last post... I would suggest the hardware raid 5 and 1 for the sas/ssd's so you don't have to worry about a single disk brining down a node....  if you don't, you basically have a raid 01 setup between the raid0 of the hdds and raid1 of the nodes, but if you do a search about raid01 you will see why it really isn't used.