Local Disk or SAN for SQL Databases?

Why should one use SAN instead of local hard disk?    I am really a novice in hardware configuration.

Some of the answers were great:

My favorite (written by Matt Whitfield):

  1. Performance. Most SANs allow you to attach extra shelves to the array, thereby giving you an easy way to up performance by throwing spindles at it.
  2. Scalability. Same reason again, more spindles = more space, as well as more performance.
  3. Redundancy. Using a SAN puts your data on a separate physical entity. SANs generally offer the facility for redundant controllers, fabric connections and power supplies. That way you can connect the SAN to multiple servers over a totally redundant fabric to achieve full redundancy. That fabric might be fibre channel, or it might be iSCSI, but either way, it’s the redundant part that counts.
  4. Maintenance. When a disk dies (which it will), then on a SAN you just pop out the old disk, and pop in the new. If you have been sensible enough to assign a hot-swap spare or two, then one of those will have already caught up with the array, and the disk you put in will become the new hot-swap spare.
  5. Flashing lights. People who look round data centres are typically impressed by flashing lights, and SANs tend to have a lot of them.

That summarized a lot of major points (flashing lights especially :)), but it’s missing a few details:

  • No mention of Automated Data Placement type features which leverage Flash drives – EMC’s Fully Automated Storage Tiering is an example of this
  • No mention of advanced protection functionality like replication and space-efficient snapshots
  • No mention of virtualization awareness and integration (Hyper-V and VMware)
  • No mention of dynamic capacity management functionality – i.e. thin provisioning

I helped write a recent Top 5 Reasons Why EMC Unified Storage for SQL Server document – and I think we did a great job capturing a lot of these details without too many words – and used some really talented graphic designers to turn my stick figures and chicken scratch into works of art.

Check it out!


One thought on “Local Disk or SAN for SQL Databases?

  1. Ratish Nair

    Hey Brian… I agree to this thought !!! Just because there exist technologies claiming SAN can be replaced by Local HDD, enterprise should not go for it…. SAN is always the best option for DR and a concept cannot replace it…

    Ratish Nair
    MVP Exchange Server


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