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Saturday, July 6, 2013

VMware boot, SD card, HDD or BFS (Boot from SAN)

There is no doubt that when it comes to reliability, the good old HDD with raid 1 or 5 will be the most reliable since it eliminates the network, switch, storage point of failure then again the server might just boot up fine if network, switch or storage (1 of the raid drive fails ) fails but you will still face the downtime of the VMs which are on a shared drive (assuming that you are using a shared storage for VMs). SD card offers a great alternative for what its worth but then your again SD card might fail (unless you have raid 1 on your SD card too) , the card reader might fail too, in any of these 2 cases your host and VMs are down.
So irrespective of SD, HDD or BFS your VMs will definitely face a downtime if the shared storage and/or the network fails. So, considering that you have already taken care of the switch part by having a redundant switch and your shared storage aka SAN is solid or near fail proof what will be the best option to consider to boot from? SD, HDD or BFS ?!
If you go with the BFS then you don't need internal storage for the servers. Let us consider a HP BL460 and if you have to order a 10 of those you will be saving a lot of money by not ordering any smart arrays with it. You can allcoate 10GB for BFS per server on your SAN. You can also eliminate the need of the physical NICs by using virtual connect or a similar network virtualization. If you take out the need of internal storage and physical NICs on the server, you are almost completely abstracting the VMware from the server hardware. You can even have a backup of the BFS lun of the server just in case you need to boot a different server with it. If you are doing a BFS them make sure you have a syslog server configured for all the hosts to store their log otherwise the BFS partition will be filled sooner than you think with all the logs of the host.

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