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Is Raid worth it

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June 10, 2009 9:40:35 PM

I am looking at buying a system that has 3 Solid state drives in Raid 0 for super speed.

Is raid worth it or is it more trouble than a benefit?

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a c 127 G Storage
June 10, 2009 9:55:57 PM

Not really.

SSDs are pretty fast themselves, and striping them won't reduce write latency on many small writes, for example. For speed, its best to buy a better SSD with better controller. The SSD controller is key to the performance, flash products exists for ~1.5GB/s transfers via PCI-express with MLC flash, its the controller that has to use the potantial of many parallel operations within the SSD. Right now, the Indilinx (Vertex) and Intel X25-M do a pretty good job, provided you can flash them to the newest firmware.

Ofcourse, its easy to buy multiple smaller SSDs and put them in RAID0 for some additional speed. Due to the reliability there is no usual RAID0 risk of disks dying. But you can face problems with the RAID-layer itself, for example it shows one of your disks as offline and you can't boot into windows etc. Those are considerations you need to take into account.

The benchmarks i've seen on high-performance SSDs on chipset RAID are that its performance scaling is limited in realistic benchmarks, 2 disks versus 1 gives some improvement, but it doesn't scale further. This is partly because of how SSDs work; if because of RAID0 one drive has to write only half the data this should mean less time required to execute, but for the SSD any write will mean a complete block erase and rewrite, unless it can be mapped to free cells like the Vertex and Intel X25-M do.

You would, ofcourse, get higher MB/s values, but those don't mean all that much to true performance.
a b G Storage
June 10, 2009 10:16:39 PM

In support of what sub mesa said, I wonder if you happened to read this:

http://www.anandtech.com/storage/showdoc.aspx?i=3531&p=...

Maybe you already know that stuff. Personally, I found it fascinating and IIRC somehwere buried in the article is some commentary on Raid you might find useful.
a c 167 G Storage
June 11, 2009 3:10:47 AM

It is probably not worthwhile.
The reason is not the raid part, but the characteristics of the underlying ssd cards. If the cards have a good controller, like the Intel X25-M then it will work well.
I have such a system. I raided two X25-M cards, primarily because I needed more than 80gb for my os drive. Honestly, it was not a big improvement over my previous velociraptor.
Cheaper ssd drives have a problem with random writes. When the writes come too fast, there may be several seconds of delay. Very annoying. The designs are improving daily, and I expect good, more reasonably priced products to appear by the end of the year. I would wait.
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