Replication is Easy, DR is hard

So here is the situation, we are looking into setting up our DR site. Of course there are about a thousand ways to go about doing this.

The most basic approach appears to be SAN replication. We love our EqualLogic SAN’s but the Delta that they transmit appears to be very heavy. People that I know that are using EqualLogic replication have very fat pipes at least 10Mbit connections or 100Mbit or of course the lucky ones use fiber.

So that next brings in WAN accelerators. It sounds like Riverbed does a decent job maybe 80 – 90 % reduction I don’t know much about BlueCoat, F5, SilverPeak or how they fair probably around that same rate. (Maybe HyperIP)

But this brings up the question whether I should be replication at this level anyways? We already are 100% virtualized so would replication at the VM level make more sense? We could use something like Veeam and maybe in conjunction with a WAN optimizer?

But then again should I just be using DAG for exchange? Is there an equivalent way to do this with SQL 2005? Or should I go with something like doubleTake ?

Also, I’m guessing that getting the virtual machine swapfile off on its own volume would be a good idea. I’m trying to figure out if its important to do anything with the paging file inside of the Guest OS?

Anyways, these are my thoughts, and questions. Anyone out there doing DR have any comments!



  1. I think a mixed approach might be best, you can use SAN replication for some VM’s and then software replication (like Veeam) for others.

    The only issue then is how are your VM’s currently setup? Since SAN is array based it can be difficult to align your priority VM’s all on the same replicated LUNS.

    Also, for WAN acceleration, take a look at HyperIP from NetEx, it’s a software based VM appliance rather than hardware.

  2. First leverage the investment and ease of use with EqualLogic Replication. You can select and schedule specific Volumes to replicate at certain times. Then you can leverage SAN HQ to better understand how much is being replicated, how long it takes to replicate, etc. Depending on your testing and findings, you may need to invest in WAN Optimization solutions. There is also tweaking VM settings and configuration such as separating and/or not including VM OS swap files, etc.

  3. Sorry I’m a bit late to comment on this but we are using both EqualLogic replication and Veeam. The benefit of Veeam is that it is crash tolerant but obviously it puts a load on the VM’s and the VMware host. The beauty of the EqualLogic replication is that it is fast and free, but it won’t always work in the way that you expect it to. Restoring from a disaster will be inconsistent from a SAN snapshot whereas with Veeam you can have a replica VM ready to go. We tend to use both depending on customer demand and what the VM is running. For a SQL server I’d suggest Veeam is the much safer option.
    You can take a look at the equallogic replication service at

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