What drives/configuration for large raid arrays

Humate

Humate

Humate

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23 Dec 2005
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652
Hi there, hope someone can help

I want to upgrade my raid array. I have a 3ware 9650-12ml raid controller running 12 non-enterprise 500GB hard drives in a single raid6 array. now at the time i built this array i had no idea what i was doing (clearly!!)... and i still dont. However, i read recently about unrecoverable read errors which made me feel uncomfortable as the way i understand it is when a drive fails in my array and i go to rebuild, theres a very high chance that i will hit a URE.

anyway, i want to buy new drives and build something with a large capacity and a high level of fault tolerance (including a low probability of failure to rebuild in the event of losing a drive).

can someone give me advice on what drives I should buy and how i should configure them? should i setup blocks of 4*3TB in raid6 or what? I want to use 3TB hard drives so i can get the maximum amount of disk space out of whatever array(s) i build (4TB is too expensive). How should i configure these 3TB drives? lets presume i will eventually be running 12*3TB but initially i can only afford 5.

any advice would be appreciated.

humate
 
no one can help? I was hoping to get the drives ordered soon. Just dont know which drives to buy and how to safely construct a large raid array having read articles online about UREs.

Thanks.
 
What RAID level would you run that provides better protection than RAID6?

The URE issue is real, but many of the articles about it are sensational rubbish.

RAID of any sort is not a substitute for having a proper backup strategy.
 
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I dont doubt i will run raid6... the question for me is how to organise 12*3TB hard drives. If i build a single 30TB array with standard consumer level hard drives, im quite sure that the probability of rebuilding such an array upon a hard drive failure will be unnacceptably low (alarmingly low in fact). I want the probability of rebuild upon failure to be >= 99.9%. so its more the fact that one would have to create several arrays with that many disks. the number and size of each array would be dependent on the quality of the drive and its given URE rate.

I think i will just have to take a harder look at google and find some of the maths to calculate the probability of successfully rebuilding arrays with a given volume size in GB.
 
I would recommend RAID10, the RAID5 rebuild time on a 3TB disk can approach 24hrs, during which time a)your entire array is at risk, and b) performance is severely degraded. The same applies for RAID6, although you can obviously lose an extra disk, but the parity calculations are even more complex than RAID6 leading to an increased rebuild time and even more performance loss.

http://community.spiceworks.com/topic/262196-one-big-raid-10-the-new-standard-in-server-storage
 
You don't mention what/how you are using your array, but is it possible to do away with raid and instead go for something like ZFS?
 
The array will just be used for storage of microscopy imaging data on my personal computer at home. So its not something that will run 24/7 and I dont require it to be fast. Reliability is my greatest concern. The data will also be stored at my work but i want my home solution to be reliable. I havent even heard of ZFS before. i will do some reading on this.

maybe i could go with raid10!! just did some reading on it and it seems like a safer option than raid6?
 
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