Questions about new NAS/SAN build...

wickedgtr

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Jun 15, 2009
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I am building a new NAS/SAN and have some questions

* = I need to purchase this

* 24 x 2TB 7200rpm 64MB drives
Areca Arc-1680ix-24 w/BBU and 2GB Cache
* Norco 4224 w/120MM Fans
Chelsio T3 10GbE Adapter
i7 930
MSI pro-e x58
12GB Ram

Future:
* SUPERMICRO MBD-X9SCM-F-O
* Intel Xeon E3-1230
* 8GB to 16GB of ECC RAM

I would like very fast sequential rates, and pretty good random I/O. I have a lot of media storage, and a VM farm for hosting applications/web servers, etc.

I am coming from an older platform very similar 'type' hardware: q6600, 8gb ram, areca arc-1261ml, 16x750gb in raid6, 10GbE and it performs okay, except for the long sequential jobs, i.e. taking 12+ hours to store 2.5TB of data. - I am also upgrading because I am out of space (selling off all the old hardware).

So now the questions:
Any recommendations for drives? I was thinking HITACHI 0F12115 Deskstar 7K3000 2TB 7200 RPM 64MB because they are reasonably fast and I can get them for ~$100 each.

With 24 drives which raid level is going to give me good data protection and good performance, I was thinking of doing a RAID 60 with 22 or 24 drives, depending on if I decide to have hot spares, or just a cold spare drive near by.

Is there any good way to start with 11-12 drives now, and easily migrate it to 22-24 drives later? I would think this question depends on which raid level is recommended.
 
What is your overall

Storage capacity requirement?
Storage IOPs requirement?
Data Paranoia requirement ?

What will be attaching to the NAS/SAN ?
 
I lost 2 drives over the weekend, during a large system backup, within a few hours of each other. I think the protection provided by RAID6 is the minimum I could deal with. I thought about doing a large RAID10, but if 2 drives die in the same stripe, I would lose everything.

I know RAID6 has slow writes, but RAID60 should at least help a little I would think -- If I am mistaken please let me know.

I currently have 12TB raw storage, ~10.5 usable, and its completely full, with about 3-5TB of data scattered on other machines, that should be on the storage machine.

I dont know my IOP requirement, most of the time its very low, but during peak times, the current san is a bottleneck.

Currently, I have 3 ESXi hosts all with 10GbE, and about 10-30 user client connections.
 
I thought about doing a large RAID10, but if 2 drives die in the same stripe, I would lose everything.

Not quite,

There are 2 x versions of RAID10

That is in your case for 24 drives it can be done 2 ways

Drive 1 + 2 < Mirror
Drive 3 + 4 < Mirror
Drive 5 + 6 < Mirror
Drive 7 + 8 < Mirror
Drive 9 + 10 < Mirror
Drive 11 + 12 < Mirror

Drive 13+ 14 < Mirror
Drive 15 + 16 < Mirror
Drive 17 + 18 < Mirror
Drive 19 + 20 < Mirror
Drive 21 + 22 < Mirror
Drive 23 + 24 < Mirror

Of which the 2 x bunches of mirrored drives (12 each) are striped across

Which is RAID 10

You maybe are thinking of Raid 0+1

Which would be

Drive 1 + 2 < Stripe
Drive 3 + 4 < Stripe
Drive 5 + 6 < Stripe
Drive 7 + 8 < Stripe
Drive 9 + 10 < Stripe
Drive 11 + 12 < Stripe

Drive 13+ 14 < Stripe
Drive 15 + 16 < Stripe
Drive 17 + 18 < Stripe
Drive 19 + 20 < Stripe
Drive 21 + 22 < Stripe
Drive 23 + 24 < Stripe

Of which the 2 x bunches of striped drives (12 each) are mirrored together

Raid 10 you could actually lose 12 drives (depending which drives) and the file system would be intact....
ie lets destroy the following drives in the 1st example

1,3,5,7,9,11,14,16,18,20,22,24

Your data is still there because it's mirrored to drives 2,4,6,8,10,13,15,17,19,21,23

Raid 0+1

Is a little less secure (depending again which drves go pop) but you could lose up to 6 drives so long as they are on the same side of the mirror. ie lose 1,3,5,7,9,11.... but if you also lose say drive 13....poof it's all over red rover.

if you are really paranoid about data loss, then you need a backup elsewhere....Raid isn't a backup blah blah.....

Else go for tripple mirrors if you can afford it;)
 
But, if I lost the 2 drives (in either method) that mirror the same data, I still lose everything right? Maybe I am not understanding correctly...

So with either raid 10 or raid 0+1 only two drives share the same bits of data right? So if I lose those 2 drives, all that data is gone right?

Does anyone know how well Raid 60 performs?

Let me know your thoughts.

Thanks,
Alan
 
Yes. Although in the above mentioned layouts you can theoretically lose 2 drives (or more)....that is only if you happen to lose just the right ones. You can't lose just any 2 drives. Anything Raid 10 you still be counted as only single drive worth of parity. With the amount of drives you plan on I would try for some kind of double parity like RAID 60 would give you.
 
and a nice controller that can handle the extra parity load...

and i know it was mentioned, but i'll reiterate-
RAID IS NOT A BACKUP
 
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