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I need to size storage array. For example i have a need of 800 IOPS, 80 MB\s and 2TB RAID 10 space.

Using this calculator http://www.wmarow.com/strcalc/ i do not understand how many 142 GB 15k drives should i have to achieve 80 MB\s. I do not understand the I\O MB\s concept.Could somoene please to explain

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1 Answer 1

You're in luck with your low volume size and easily achievable overall throughput requirements but your (presumably random) IOPS target needs a bit of thought.

I'm a huge fan of Seagate's Cheetah 15k 3.5 SAS disks for this balance needs - in particular their ST3600057SS which is a very robust 600GB/16MB 6Gbps disk that's good for minimum of 150 IOPS across a broad range of IO types.

If you take that as an assumption and don't count on R10 actually helping with performance (it will of course but I never bank on it) then you end up with needing 5.3 disks to hit 800. Given the 150 was a negative figure I think you'd happily get away with two banks of 5 of those disks and be certain you'd get 800 really consistently.

If you wanted to though you could use two banks of 4 disks and test it, you may find you only get around 700-750 but depending on the methodology you've used to get to the 800 figure this configuration may well give you what you need and save you two disks.

If you're looking for hardware RAID I'd happily recommend Adaptec's 51645 adapter for this kind of work.

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+1, I've got a pile of Cheeta 15k 3.5 SAS drives (re-branded as HP); and I can also attest to their performance. The Adaptec card is also a excellent one, I use one just like it in my home array (we're all HP at work, so Smart Arrays all around). –  Chris S Jul 28 '10 at 13:25
    
I prefer HP SA's too but if you're not a HP person then the Adaptec's are a 'safe pair of hands' in my opinion. I've got walls and walls of those HP-branded 15k's in EVAs all over and they really are a great disk, though I detest the 1TB FATA EVA disks, they die quicker than fairground goldfish. –  Chopper3 Jul 28 '10 at 13:46
    
Ok, this did not explain whether and how to take MB\s in mind when choosing disks for storage array. This information i need the most –  aurimask Jul 30 '10 at 7:11
    
Basically don't worry about it, all disks in the volume you need will keep up. –  Chopper3 Jul 30 '10 at 7:50

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