Oracle-L: Re: SAN - Oracle - Pitfalls

From: Bill Pass <wbpass_at_yahoo.com>
Date: Fri, 14 Jun 2002 13:43:18 -0800
Message-ID: <F001.0047E9B8.20020614134318@fatcity.com>

I like SAN's for alot of reasons and if you are using them in a traditional non-replicated environment, they work well. Just don't buy into the sales hype that you don't need to do phsycial database design because we have should big caches etc... Those big caches are great for improving write performance, but don't help that much on heavy random read activity. I have seen very poor performance on very large EMC arrays due to this mentality, so do your homework.

The remained of this e-mail deals w/doing block (or track) level replication between SANS...

The only method of "real-time" block level replication supported by oracle is synchronous. So you need to worry about the impact synchronous replication will have on your transaction stream (especially log buffer writes). For EMC, they only ship entire tracks, so this really slows down log writes as you end up shipping the same track over and over again synchrounously to the remote EMC boxes memory. Also, there are limits on the number of hops between the two locations and transport delay (speed of light is a factor). About the only way it makes sense is if you can pull dark fiber between the two sites.

If you can afford to lose some transactions, then you can use a split mirror approach (EMC has another product called timefinder which is useful here). This approach does not impact your online transaction stream and is less demanding from a network perspecive.

Both of these solutions are cool black box solutions that a DBA doesn't need to worry about. My own opinion is after reality sets in and you realize that the synchronous approach will not work, why not just go with DataGuard. Same bennefit at a fraction of the cost.

Bill

"Mandar A. Ghosalkar" <mghosalk_at_byer.com> wrote:
> Hello Guys,
>
> any guys here who have SAN. We are inviting a SAN
> vendor for possible solutions for our enterprise.
>
> i am unaware about how SAN would affect me as DBA.
> Also we are thinking about how we can use OS level
> block replication between two database servers
> located in different cities(SF and LA).
>
> any suggestion about pitfalls?
>
> TIA
> Mandar
> --
> Please see the official ORACLE-L FAQ:
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> --
> Author: Mandar A. Ghosalkar
> INET: mghosalk_at_byer.com
>
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-- 
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-- 
Author: Bill Pass
  INET: wbpass_at_yahoo.com

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Received on Fri Jun 14 2002 - 16:43:18 CDT

Re: SAN - Oracle - Pitfalls - Adv/Disadvantages??