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DIY Storage Part 2: Picking the Right SAN Software
This is the second installment in a series on building your own SAN. In part 1 I discussed why I decided to build my own array as a pilot project, and laid out the hardware specs.
In this post, I'll talk about how I choose the storage software to run on the machine. I looked at a variety of options, including open source and commercial products. Ultimately I chose Windows Storage Server 2012. Here's why.
I started with open source software including Openfiler and FreeNAS, but I had concerns with each. I had heard several user reports of unreliable performance with Openfiler's native iSCSI target driver. This was substantiated to me by the fact that Openfiler offers a $1,000 enhanced iSCSI module as a paid option. Plus, I found Openfiler's configuration menus to be cryptic, and setup was intensive--as many who have dabbled in open source applications can probably relate. That said, I believe Openfiler's commercial offerings are robust enough for enterprise use.
As for FreeNAS, it has limited capabilities. I wasn't looking so much for NFS as I was for teamed, gigabit, iSCSI multi-path I/O for storage uplink. Even though the SAN I'm building is a pilot project for non-mission-critical backup, I still wanted enterprise features.
On the paid side, Nexenta was my first stop, and I was excited to look it over. Why? Because Nexenta uses ZFS as its background file system. Solaris aficionados will tell you that ZFS is powerful stuff. Not only does it support a huge variety of RAID types across controllers and disparate drives, but it also supports native de-duplication and compression.
I evaluated Nexenta in a virtual machine to see how it shook out. Configuration is pleasantly simple. It supports VMware and Hyper-V, block-level mirroring of data, unlimited storage, and SSD caching. In addition, it supports FC and iSCSI MPIO, and as far as price goes for paid solutions, it's pretty reasonable.
But there are a ton of other options. The Cadillac of BYO SAN software is Datacore's SanMelody, which has recently been revamped and more economically licensed as SanSymphony. SanSymphony runs on top of a Windows server, and offers everything you expect from a Tier-1 SAN. In addition, it supports active/active controllers with cluster services on dual-node, shared backplane boxes, so you can build a dual-controller, fully redundant SAN. The downside is that you pay for Windows licensing on top of SanSymphony itself, which can be pricey, especially if you want all the bells and whistles.
Starwind makes a surprisingly inexpensive and mature iSCSI DIY SAN software package that also runs on Windows servers. You get snapshots, thin provisioning, active/active clustering, MPIO, and data dedupe for free! You only pay for replication services and large disk caches. This gives you the option of installing the software and getting a really good feel for it before buying, and it was my runner up for the OS on my SAN.
Finally, HP makes a product called StoreVirtual VSA. It runs on virtualized servers, making local disk space available to form multi-element striped member storage. So if you've got vSphere on a ton of boxes running on twin 400Gbyte SAS in RAID 1, why not take that 370+Gig of RAID 1 data and turn it into enormous, multi-box network volumes with HP's software? It's a bit of a specialty but it works, and if you're an HP shop or large enough, it may be a nice value proposition to create a whole other tier of storage out of wasted space.
In the end, however, Windows Storage Server 2012 won out. One reason is that because I'm using this little array in an evaluation sense, I was entitled to use my Technet Pro subscription to license SS2012 for evaluation purposes.
SS2012 installed easily, detected all the storage in my machine, and created redundant RAID sets across dissimilar-sized drives running on multiple controllers. Provisioning these disk pools into discrete volumes was easy, and it was even easier to set up as iSCSI or NFS targets for VMware ISO sharing, or auxiliary disk space. Multi-path iSCSI I/O works great, and I'm impressed with the management tools that Microsoft provides with this latest version.
SS2012 has snapshots, de-duplication, dynamic volume expansion and thin provisioning, which is the basic feature set I required. As you might imagine, it's slightly friendlier to Hyper-V than VMware (snapshot features are more sophisticated on VHD files), but it's a pleasure to install and use. I was up and running in about an hour and had a few VMware hosts connected to a couple iSCSI volumes.
What really won me over is that SS2012 is an enterprise-level product. It supports replication with Remote Differential Compression and built-in Microsoft tools. It can be configured on two-node systems with cluster services to provide active/active, fully redundant SAN configurations.
Licensing costs aren't out for this product yet, so if you don't have Technet, you are out of luck. But I am hoping that licenses are reasonable, because this software dovetails nicely into a Windows 2012 server infrastructures and delivers excellent performance even on minimal hardware.
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