Mar 26, 2012
tom

24TB RAID 6 configuration

Question

I am in charge of a new website in a niche industry that stores lots of data (10+ TB per client, growing to 2 or 3 clients soon). We are considering ordering about $5000 worth of 3TB drives (10 in a RAID 6 configuration and 10 for backup), which will give us approximately 24 TB of production storage. The data will be written once and remain unmodified for the lifetime of the website, so we only need to do a backup one time.

I understand basic RAID theory, however I am not experienced with it. My question is, does this sound like a good configuration? What potential problems could this setup cause?

Also, what is the best way to do a one-time backup? Have two RAID 6 arrays, one for offsite backup and one for production? Or should I backup the RAID 6 production array to a JBOD?

EDIT:
The data server is running Windows 2008 Server x64.

EDIT 2:
To reduce rebuild time, what would you think about using two RAID 5’s instead of one RAID 6?

Asked by Phil

Answer

I currently support 220 servers up to 96 TB (totalling 2 PB or so), some in clusters of up to 240 TB, that my team built. Here are my advices :

  • use a good, reliable hardware RAID controller : possible choices are 3Ware 96xx or 97xx, LSI 92xx, Areca 16xx, Adaptec 5xx5… Of course, with a Battery Backup Unit because power failures occur sometimes.
  • use only professional grade drives,coming with 24/24 and 7/7 operation support; don’t use cheap desktop drives. You don’t want to lose 100,000$ worth of data because you chose to save 20 bucks per drive.
  • The biggest the drives, the longer the rebuild. 3 TB will need at least 12 hours in the best case. Use RAID-6 for reliable protection.
  • drives do fail. Up to 5% per year; don’t even dream of using JBOD, even for backup. This is plain bad advice. Use RAID-6.
  • RAID-5 is obsolete, we simply don’t use it anymore with drives bigger than 300GB.
    See this expert post for instance. Did I mentioned you should use RAID-6?
  • For only 24 TB, I’d stick to 2 TB drives; there is a 10-15% premium on 3 TB; more spindles will provide better performance, shorter rebuild, and better safety because the drives have been available for quite a long time and are really very reliable.
  • You could buy an excellent 3U Supermicro, AIC or equivalent chassis with 16 drives slots, filled with 2TB drives (RAID-6 + hot spare) that would provide exactly 24 TiB of available space and redundant power supplies.
Answered by wazoox

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