Viji V Nair wrote:
There are catches in the SAN controllers also. SAN vendors wont give that much information regarding their internal controller design. They will say they have 4 external 4G ports, you should also check how many internal ports they have and the how the controllers are operating, in Active-Active or Active- Standby mode.
Right, the SAN cache serves the same purpose as the controller cache on direct-attached storage. I've never seen a Fiber Channel card that had its own local cache too; doubt that's even possible. So I think of them as basically being the same type of cache, with the primary difference being that the transfers between the host and the cache has some latency on it with FC compared to direct storage.
You're right that people should question the internal design too of course. Some days I wonder if I'm in the wrong business--the people who do SAN tuning seem to have no idea what they're doing and yet are still expensive to hire. But this is off-topic for the question being asked here.
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