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Building a 12-disk software RAID6 - is this setup feasible?


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#1 mcenno

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Posted 12 April 2013 - 04:22 AM

Hello,


I need to create storage out of 12 new 3TB drives (which I couldn't use in one existing server, so I'm now moving to another). Any feedback on this setup is much appreciated.

The dominant boundary condition is cost. I'm trying to keep the budget below 200 Euro. The goal is to create a 12TB RAID6, predominantly to store large data sets, ie, performance is not a strong driver (a minimum throughput of 100MB/s would be really good, anything higher would be great).


Here is the existing hardware:

-a case with 12 empty bays, without backplane but sufficient power and cooling
-out of the 6 available on-board SATA2 ports, 4 are occupied
-the board is a ASUS Z8NR-D12 (http://www.asus.com/...tations/Z8NRD12) with an Intel Xeon 4-core processor (8 using hyperthreading) and 24GB of memory.
-12 Hitachi HUA723030ALA640 3TB drives


I'm thinking of buying two SATA adapter cards to attach the drives to it and to make the RAID6 in software (Linux' mdadm tools). I deem the machine to have sufficient punch to deal with the extra load, and since there won't be any massive parallel computing I expect that there will always be a core or two available to handle the RAID6.

So for example I could buy a Supermicro AOC-USAS2-L8i (see http://www.supermicr...2-L8i.cfm?TYP=I) which is of order ~150 Euro, but still requires 2 SFF8087 breakout cables for ~40 Euros, but we have these two somewhere. In addition I'd need a simple 4-port SATA controller, or a very cheap 2-port controller plus use the remaining 2 available on-board SATA ports.

So that would result in 12 available SATA ports to which to connect the 12 drives. I'd then use mdadm to create a RAID6 array.


Does that sound feasible?


Regards,

Enno

#2 continuum

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Posted 12 April 2013 - 01:53 PM

Should work, assuming you don't hit any driver weirdness. I assume you'll be running ZFS?

#3 dietrc70

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Posted 13 April 2013 - 01:28 AM

I'd just add that you should be sure to get real enterprise HBA's (like that LSI you mentioned). Two LSI models with the same chipset would be ideal. I've seen 16 port HBA's but they cost a fortune.

Don't mix some cheap consumer SiI/Jmicron SATA card into your array. That would be a serious weak link. The SFF-8087 cables and connectors are much better made than consumer SATA cables and are worth the expense. The onboard Intel SATA is excellent, but I think it would be better to have the RAID on dedicated SAS/SATA HBA's that use the same driver.

The best aftermarket backplane I've used is the Supermicro M35T or the managed backplane M35TQ (5 drives in three bays). They are built like tanks and have activity/failure indicators and great airflow.

I understand your concern with cost, but if you want to make a 30TB array with several thousand Euro's worth of hard drives it would be very unwise to cut corners on HBA's, cables, or enclosures.

Edited by dietrc70, 13 April 2013 - 01:29 AM.

#4 mcenno

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Posted 16 April 2013 - 06:32 AM

Hello,

I assume you'll be running ZFS?



Why would I use ZFS? The RAID6 functionality would be taken from mdadm. Does ZFS under Linux perform better/more convenient/more reliable than mdadm?


Enno

#5 mcenno

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Posted 16 April 2013 - 06:35 AM

Hello,

I understand your concern with cost, but if you want to make a 30TB array with several thousand Euro's worth of hard drives it would be very unwise to cut corners on HBA's, cables, or enclosures.



Good point. Yes indeed it would be stupid to spoil things with cheap controllers. I think I'll get an LSI SAS 9201-16i (4 x SFF8087 -> 16 x SATA). I hope it's within the budget (which is not under my control).


Cheers,

Enno

#6 MRFS

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Posted 01 May 2013 - 09:49 AM

Areca PCIe controllers also support RAID 6.

Also, some SFF-8087 fan-out cables are 1.0 meter in length,
and that can cause some cable management problems,
especially when your HBA has 4+ ports.

The StarTech version is 0.5m (one-half meter).


MRFS



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