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I am looking at re purposing some hardware and build out a virtual environment. I am looking to use the LeftHand VSA (Virtual Storage Appliance) to serve the local disks as a SAN to the virtual machines.

The heaviest app would be a Microsoft SQL database with 50 concurrent client connections, pulling light medical records.

Does anyone have any real world experience with the product and what is you take on it?

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Are you putting the SQL DB and log files on the VSA? –  Rob Bergin May 4 '09 at 2:34
    
I was planning to. I am still formulating my plan of action. –  Keith Sirmons May 4 '09 at 17:08
    
Typical SQL database size is around 50-60GB –  Keith Sirmons May 4 '09 at 17:09

4 Answers 4

up vote 3 down vote accepted

Before I talk about LeftHand's VSA specifically, I'm going to zoom out and talk iSCSI in general. If you're going to hook SQL Server up over 1 gig iSCSI, then your max storage bandwidth is 100MB/sec - fairly low. It's pretty easy to saturate that with a handful of hard drives. SQL Server lives and dies by IO speed, so as a result, I don't see a lot of production SQL Servers running entirely on iSCSI. I love iSCSI, don't get me wrong, but it's pretty easy to hit the bandwidth ceiling.

You can add multiple network ports and start doing multipathing, but you have to be careful: most multipathing solutions out there aren't really active/active, but active/passive. You can do some delicate setup operations and split out load - for example, use one array for your data, one for your logs, and use different network cards for the "active" pipe for each array. However, that's a manual setup, and you have to stay on top of that manually.

Now, let's talk LeftHand's VSA: not only are you facing these bandwidth limitations, but now you're going to lose some speed off the top due to the overhead of a software SAN implemented through virtualization. The network throughput is virtualized, the storage access is virtualized, and the cpu/memory is virtualized - whereas SAN gear is built from the ground up for IO speed.

Does it work? Absolutely. Is it as fast as conventional SAN gear? No, and in some cases, it's not even as fast as direct attached storage.

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We did a trial of the VSA and decided against it; it performed poorly for SQL. If your usage for SQL is pretty light, it would work ok but there are much cheaper solutions.

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I would think small SQL - less than 2 GB might be okay - but large SQL wouldn't perform as well as on physical disks. –  Rob Bergin May 4 '09 at 2:35

Presumably you're looking at LeftHand for it's price. If so then I couldn't agree with Brent Ozar any more, SQL lives and dies by its latency and iSCSI is all about price/performance - not performance. I would look to an inexpensive FC SAN such as the HP MSA2000fc, I'd be surprised if it's much more expensive that the LeftHand (especially as you're dealing with HP already and they're very grateful of orders right now, expect big discounts) and will perform MUCH better today and in the future.

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Price is one reason. The "Full" software suite is an other. I also like the method of Network Raid for redundancy. –  Keith Sirmons May 5 '09 at 2:37

I know this is an old question but thought I would comment. I use dual VSA's via two VMWare boxes. The speed is MUCH slower than our true P4500 units. I use the VSA's at our Disaster Recovery site mostly for backup so it is fine for that (and works great), but I wouldn't use it for true production servers. I have 1 VM server (a web server) running on our hardware there and it dogs down considerably when remote snapshots are being pushed to it.

This all depends on the underlying hardware that you are using also of course. Plus, I started out with 500GB drives, then upgraded to 1TB drives, and just recently re-installed everything and went with 2TB drives (5 drives in each server). As I moved to bigger drives the performance was negatively impacted as would be expected. But I was looking for more storage for remote snapshots. My concern now is that if we ever recover to that site in the event of a disaster I fear everything will be very SLOW. I will probably be upgrading to true units soon (perhaps used from eBay).

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