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Migrating from DAS to a SAN

I am looking at migrating from DAS to a SAN. The initial configuration will include three Windows 2003 enterprise clusters to store all data on the SAN. The second level will be to add Unix servers, Oracle databases and HP OpenVMS systems to the SAN. The SAN will start out with 4 terabytes (TB), two for production (FC drives) and two for mirror or snapshot. (SATA or FATA drives). Over the next two years, it will grow to 30 TB.

One configuration I looked at included:

  • Two FC drives -- RAID-5
  • Two SATA drives -- RAID-5
  • Full redundancy dual 16 port switches and dual single port HBAs in servers with load balancing software.
  • Basic managing software and snapshot software

    The second configuration was the same as above with 4 TB HP EVA5000 system combination FC drives and FATA drives managed by the OS.

    The OS managed system sounds good, but are the FC and FATA drives a two-tier solution or is it just 4 TB of storage, with no way to enhance performance or load balance?

  • Either configuration should work for your initial requirements. The first solution would provide discreet separate components, which would allow you to place the SATA array at distance from the production FC array. The second solution would provide two pools of storage within the same enclosure.

    Both provide a method of tiered storage, since the virtualization within the EVA can configure the different drive types as separate pools.

    As for flexibility and performance, you can configure different RAID types within the arrays to match the applications requirements. RAID-1 or RAID-10 is best for log file storage, and RAID-5 can house database-type storage. This would give you both two tiers of performance and two tiers of storage classes. Load balancing would be done at the host side using the path failover software. If you use volume management on the host side, you can stripe your LUN access across both HBAs for best performance.

    You mentioned 16 port switches. Since you also said your growth within the next two years would almost quintuple your requirements (from 4 to 30 TB, and addition of Unix and VMS servers), I would start out with more ports in the switches (Perhaps dual 32 port switches). If your budget does not allow for larger switches, then make sure the ones you buy will support zoning and trunking. As the SAN grows and you add more switches, you don't want to have to include multiple hops and many ISLs (inter-switch links). Moving to larger CORE type switches may be a better way to grow. Also note that Unix, VMS and Windows servers should be placed in separate zones within the fabric.

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