Ask the Expert

Configuring your first SAN: Ten advantages

For a small-to-medium sized company with 12 servers (no failover server), I want to create a mirror/snapshot of the system drive -- OS + database + application server settings. The reason is, that after a server and an OS go down, reinstallation of an OS + application server + database server takes twice as long (four hours) as restoring database from database backup files (two hours).

How will a SAN help in this case? We have 14 (73 GB, 10K rpm) internal disks per server for a total of 164 disks. Is $150K a reasonable target for moving all the disks into a SAN with tape library support, with currently having seven DAS tape drives -- one tape drive per two servers -- for a total of five TB data full backup in the weekend and 0.3 TB incremental every weeknight?

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Click here to go back to part two of this series, Configuring your first SAN: Creating your LUNs.

So what does all this buy you? Ten things.

  1. If a server fails, you simply roll in a new server, move the HBAs over from the failed server and reboot. You're back up in minutes!

  2. You can automate all your backups to the shared library using FULL every night. This allows faster restores and since backup is over the SAN, it happens at 200 MB per second over the fabric. Your bottleneck will be your tape drives, not the network.

  3. You can now utilize all the storage you've purchased and provision it better for the servers that need it. This will lengthen the time between storage purchases, and give you that 60% of wasted storage back!

  4. No more server downtime to add disks.

  5. You now have two paths to storage, making your applications more reliable.

  6. Your applications will run faster over the SAN, since you have 400 MB per second access to data.

  7. You can spread your I/O load across multiple RAID5 LUNs in the storage array, which will let you handle multiple drive failures.

  8. Most SAN arrays have automatic sparing, so if a drive does fail, your servers never notice and the applications stay up.

  9. You can take advantage of storage array-based data replication for disaster recovery.

  10. Since your disks are now shared, you can implement host-based clustering to increase your application uptime and reduce operational headaches on hardware or application failure.

By the way, Chapter 10 of my book "Storage Area Networks for Dummies" has the step-by-step procedures for creating a boot disk in the SAN.

Editor's note: Do you agree with this expert's response? If you have more to share, post it in one of our .bphAaR2qhqA^0@/searchstorage>discussion forums.

The views and opinions expressed by Christopher L. Poelker are his alone and not necessarily shared by Hitachi Data Systems.

Click here to go back to part one.

This was first published in June 2004

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