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SAN vs. Internal Storage

Former Member
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Hi All,

I'm in the process of upgrading our servers to Power Systems 595s. Part of this upgrade will replace most of the disk in each server so if I were to convert to SAN, this would be the time to do it. If anyone is running their SAP systems on IBM SANs, please provide some information on the experience (performance, reliability, administration, etc.)? I would probably use a basic configuration aand continue with MIMIX replication initially.



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Answers (3)

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Hi Stan,

we are using since (more or less) 6 years external storage together with System i (iSeries) and SAP.

I would agree to Carstens statement, may be internal disks are still a little bit faster. The question is: will you notice it if your SAN design is set up properly?

If you follow the rules (disk arms, how many systems per HBA..) you will not feel a difference.

We are working a long time with external disks and I would not miss the benefits of it (adding disks to any time I like, moving from one System i to another in between 1 hour downtime, etc.)

best regards, Christian

Former Member
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With the new IOA's IBM introduced performance should not be a problem. If you google "henry may ibm sansone" you should find first hit a recent IBM white paper that discusses this. It is not SAP related, but hopefully should allay some of the fears.

DS8000's are big. The installation will cause some upheaval in the computer room, some more infrastructure/fabric, require new skills but they are enterprise strength disk subsystems, allow storage flexibility & consolidation and will bring with them new (and perhaps stronger) options for your DR & HA environments. The external storage being a SAN, they will open up other systems in the data center to this class of storage, and assuming there is a high speed tape subsystem in there somewhere they will benefit from that.

While not all customers have the same requirements, internal disks normally bring ease of management and ordering, a lower total storage solution price, balanced performance and a convenient packaging structure.

Hope this helps.

Former Member
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I am discussing some years about this topic.

In 2007 there was an inofficial statement from IBM that the internal disks with the fast controller in the EXP 24 are a bit faster then DS8.

I think this is true. But disks performance depends to so much parameters.

In 2009 i want to have a storage to a new Power System, because whith no Load Source it is very easy to switch to a new machine. I think the trick for a good performance is to have enough disks arms. It is very important to keep an eye to the i/O per second on every disk. For this it is good to have Performance Tools on i5/OS.

I have talked to a guy who has so many disks, that he have only 40 - 50 % system ASP used.

But he wants to have many disks arms, or in the language of DS8 many loons.

Then the disks requests are very fast.

So I think a storage is good for changing machines, good for expansion and good for performance, if you do it right.

best regards,

Carsten Schulz