To SAN or to VSAN, that’s the question

Just a few thoughts.

As you probably all heard, VMware has announced the availability of there VSAN now integrated in the vmkernel of the vSphere 5.5 suite. If I read the specification and serveral blog post I get real excited. But is this the end of the SAN?

You probably all know the (dis)advantages of a traditional SAN, so I won’t sum this up. The next question is: When is a VSAN better than a traditional SAN? In my opinion a VSAN becomes interesting when it a can do the following:

  1. It has to be as or faster than a traditional SAN.
    If you look at the architecutre of the VSAN you probaly would say that it’s faster than a traditional SAN because you have local disk. Much will depend on a mechanism that a vSphere host will always access a virtual machine rom his local storage. If the virtual machines is on a other vSphere host you will access a traditional SAN. So this concept has to prove itself
  2. It has to be the same or cheaper than a traditional SAN.
    This really depends on the size of you storage and what kind of features you want to use. So this can be a advantage of disadvantage for both. I think that for most companies the VSAN will be cheaper, but if you need a large amount storage, VSAN will be more expensive because you need 3 times the amount of disks. And this all has to be replicated with 10G. I agree that 10G in the datacenter is the future, but at this time is to expensive for most companies.
  3. It has to be easier to administer than a traditional SAN.
    This is a fact. A VSAN is easy to administer. But don’t forget that this is a fact because a VSAN doesn’t have the options as a NetApp or 3PAR, EMC etc.
  4. It has to have the same extra options (replication, HA, application awareness, backup, duplicate block tracking, etc) as a traditional SAN.
    This one is simple. VSAN doesn’t have all the extra option that you could buy with a traditional SAN. For me application awareness for backup purposes is a real issue. If this feature could be added to the VSAN software it would great!
  5. It has to be more green as a traditional SAN.
    One of the benefits of virtualization is that you need less physical hardware. Less phusical hardware meens less power consumption, less rackspace and less cooling (witch result in less power consumption). With a VSAN you won’t use a 1U server because of the lack of disk bay’s. So you probably will switch to 2u or 4u severs in larger environments.  As you need a least 3 hosts for replication a VSAN will use more power, rackspace and cooling. Of course, a traditional SAN also uses rackspace, power and cooling, but you won’t need 3 times the disk. At the most 2 times in most configurations.

I don’t want to sound to negative about VSAN. Actually I’m quite excited and see a lot of potential. But I also see disadvantage and don’t thinks a VSAN is the solution for all our storage problems. But I’m convinced that with the next release of VSAN, these disadvantages will be solved and that a VSAN  (doesn’t matter form witch vendor) is the future.



About Michael
Michael Wilmsen is a experienced VMware Architect with more than 20 years in the IT industry. Main focus is VMware vSphere, Horizon View and Hyper Converged with a deep interest into performance and architecture. Michael is VCDX 210 certified, has been rewarded with the vExpert title from 2011, Nutanix Tech Champion and a Nutanix Platform Professional.

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