Re: RAID5 - to split or not to split

On Sunday 10 June 2001 16:15, Mogens Nørgaard wrote:

> It becomes really absurd when you look at the SAN offerings on the market.
> For instance, IBM's Shark only offers the customer the choice between JBOD
> (Just a Bunch Of Disks, ie., Non-RAID) and RAID5. IBM has a red book out
> regarding this and on page 127 out of 228 or so you can read the headline:
> "JBOD or RAID5?" and that's when it dawns on you that Shark (which is very
> expensive) cannot under any circumstances be configured for anything else
> than RAID5 or non-RAID. Workaround: Place a file system on top that at
> least can be striped (Veritas, for instance).

I've worked on the Shark systems. They're are pretty fast, especially when you're used to 5 year old Sun SSA's. :)

It was disconcerting to discover that the only HA disk array was RAID 5.

I didn't have any say in the vendor however. It is important to work with the vendor and your storage admin on the configuration of these, otherwise they *will* give you one very large disk volume to work with.

Their idea of benchmarking is 'how fast can I read a single file'. I'm not making this up. :-(

One thing to watch for on their throughput numbers as well. You have to do the math, cuz they won't do it for you.

If you examine them carefully by examining the max disk throughput and the cache throughput, you'll see that the only way to achieve their claimed throughput rate is with a near 100% cache hit rate.

And we *know* about cache hit rates, don't we folks. ;)

I didn't get the chance to stress test this system, it would be nice to hear from someone that has pushed the Shark to the limit.

Jared

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Author: Jared Still
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