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Re: why SAN ? why not external storage ?

From: Tim Gorman <Tim_at_SageLogix.com>
Date: Wed, 12 Mar 2003 09:18:03 -0800
Message-ID: <F001.00567BBA.20030312091803@fatcity.com>


Dick Goulet gave an excellent response to the list earlier -- I'd second him on each point he made.

There is no doubt that DAS is cheaper on the original purchase, because you're only buying the disk. Obviously, a SAN has a few more bits of iron and wire. But have those administrators toted up the cost of tying storage directly to servers over time? Without the ability to shift storage from server to server as needs change? As you migrate services (like databases, like shared drives, like email) from server to server, can you always migrate the storage? Or do you have to buy new storage for the new server? Oh, and once you buy the new storage, how are you going to move the data? Over the LAN?

People who are used to administering web servers and application servers don't think much about storage. A server is a server is a server. A server has disk attached. You can add to it. What's the problem? The problem starts when you start to have lots of servers that require lots of storage, and the services (a.k.a. applications) that they support change over time. They grow. They consolidate. Servers reach end of life. CIOs read a magazine article and get a wild idea.

If you don't have a lot of storage-intensive servers (such as database servers) and a CIO who sticks to financial journals, then a SAN is overkill.

I've not seen any evidence of performance problems with SANs, as opposed to DAS. I'd be interested to see numbers. A storage-area network (SAN) is merely a virtualization layer atop a bunch of direct-attach storage (DAS). If the underlying DAS is fibre-connected, then the SAN should be fibre-connected throughout, whereever appropriate. Of course, if the SAN head is connected to servers via 100Mb/s Ethernet instead of fibre (or some other obvious misconfiguration), there will be a problem. But attributing performance problems to the SAN virtualization is kind of like the old arguments when RAID0 was new (i.e. "all that CPU expended to keep track of the scattered blocks across all those drives will make performance worse, not better!").

A SAN is more complex on initial setup than just buying another DAS, but the sysadmins have to learn to keep up with technology also...

> Tim - Can you elaborate on those reasons? Our administrators feel DAS is
> usually much cheaper, and they are not convinced the SAN performance is
> there.
>
>
>
> Dennis Williams
> DBA, 40%OCP, 100% DBA
> Lifetouch, Inc.
> dwilliams_at_lifetouch.com
>
> -----Original Message-----
> Sent: Wednesday, March 12, 2003 7:34 AM
> To: Multiple recipients of list ORACLE-L
>
>
> Can you share some of the reasons related to your decision in choosing a
> direct-attach storage (DAS) instead of a SAN? In general, a SAN is a much
> smarter choice than DAS.
>
> ----- Original Message -----
> To: Multiple <mailto:ORACLE-L_at_fatcity.com> recipients of list ORACLE-L
> Sent: Wednesday, March 12, 2003 1:33 AM
>
> list, one of our clietns are going to by SAN, the current oracle databases
> take around
> 36GB of storage.... i dnt understand there reason to go for SAN, i
> sugguested to buy an external storage
> box instead. How can i justify my desicion ? (cost of not the factor)
>
> TIA
> rahul
>
>
>
>
> --
> Please see the official ORACLE-L FAQ: http://www.orafaq.net
> --
> Author: DENNIS WILLIAMS
> INET: DWILLIAMS_at_LIFETOUCH.COM
>
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-- 
Please see the official ORACLE-L FAQ: http://www.orafaq.net
-- 
Author: Tim Gorman
  INET: Tim_at_SageLogix.com

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Received on Wed Mar 12 2003 - 11:18:03 CST

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