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My website is driven by mysql db, nowadays, the db has grown more than 100G. Each time I feel headache when upgrading the server. My vendor suggests using a SAN instead directly attached internal disk, meanwhile, they advise SAN is faster and safer than disk.

I have no experience on SAN, I'd appreciate any experienced advise on whether SAN is better solution for storing db? Thanks.

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migrated from stackoverflow.com May 17 '11 at 10:07

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3 Answers 3

I would recommend a SAN for the following reasons:

  1. High availability of disks and redundancy of data.
  2. Some sort of replication/mirror technology is storing your data in multiple locations on a SAN.
  3. SANs come with their own processing, memory, etc. freeing up server resources to focus on queries, inserts, deletes, etc (in your example for MySQL).
  4. Generally a higher back plane and communication pipe via fiber, etc.
  5. Snapshot technology is available on most SANs that I know. This allows you to take real time snapshots of data saving a point in time to redeploy or back it up.
  6. On some SANs you can lose up to 12 disks or more and your data is safe and intact.

I think in addition to the above you need to ask the business questions.

  1. Is cost a factor?
  2. In what we do, what do we gain from using a SAN vs. DAS?
  3. Do our SLAs or obligations require us to have a level of availability/uptime that a SAN would provide over DAS?

You get the point. :)

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  • SANs can be faster or slower than DAS.
  • SANS can be safer or less safe than DAS.

Comparing there two things can be done but only with the full information available - what is your existing server (hardware, OS, FS, environment etc.), how is its DAS setup, how does it perform today? you need to know these answers.

Then you can look at the proposed SAN and ask the same questions about its setup and performance.

Only then will you know.

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Although rather a simplification, SANs are mainly used - in large scale deployments where you want to manage your storage separately from your "CPUs" and have hi-end features such as replication, snapshots etc. - in virtual environments where you want to be able to migrate VMs between hosts without downtime

I suspect that in your case, the switch to a SAN would not provide any worthwhile benefits if it is simply for a 100GB MySQL database.

It is certainly not the case that SANs are necessarily safer or faster - but of course it depends on what you spend - an expensive SAN will be better than cheap DAS and visa-versa but in general SANs are more expensive than DAS solutions but give better features etc.

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