Monthly Archives: July 2012

Which Hot Spare will be used for a failed drive? (EMC Clariion / VNX)

Hard Drive

How does an EMC Clariion or VNX decide which Hot Spare will be used for any failed drive?

First of all not the entire failed drive will be rebuilt, but only the LUNs that reside on the failed drive. Furthermore all LUNs on the failed drive will be rebuilt to the same Hot Spare, so a single failed drive will be replaced by a single Hot Spare. So if for example a 600GB drive fails with only 100GB worth of LUNs on it, in theory a 146GB drive could be invoked to rebuild the data. The location of the last LUN block on the failed drive specifies how large the Hot Spare needs to be. If on a 600GB drive the last block of the last LUN sits on “location 350GB”, but the amount of disk space used by all LUNs residing on that drive is 100GB, the 146 and 300GB Hot Spares aren’t valid choices, since the last block address is beyond the 300GB mark (350GB). So valid Hot Spares would be 400GB or larger.

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Facilitate the conversation: say what you mean and don’t make assumptions

We all work with words every day. Words that can cause confusion if used incorrectly, but words can also make the conversation smoothless … if used correctly.

I’d like to name a few of these possible confusion from my daily experience in the IT Storage business.


  • Network versus fileserver

How many of you store their data on the network? The network connects clients to servers (or other clients). The network consists of network devices like switches, routers, bridges, firewalls and the cables to connect all these devices together. I store my data on a file server and the network helps me getting it there.

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