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ZFS Pool Expansion Options

Posted: 08 Dec 2013 04:11
by PCgeek215
Hi All!

I currently have a ZFS pool with 4 x 1.5TB drives that has basically filled up. I'm currently on FreeNAS 0.7.2 5543 but I'll upgrade to N4F latest before attempting to expand anything.

What I'm looking to do is expand this storage with an additional 5 x 3TB drives, so far I think the best way to achieve this is to add a new vDev with the new disks in a RAIDz configuration and add it to the pool. I know the current recommendation is to use the same number of drives when adding a new vDev but i'm not seeking an increase in speed as the current performance is adequate.

Is there a better way?

Re: ZFS Pool Expansion Options

Posted: 08 Dec 2013 04:46
by Onichan
There shouldn't be any issue with doing that. It isn't optimal, but won't hurt anything and most likely your LAN or CPU will be the bottleneck anyways. Though personally I wouldn't recommend only 1 drive of parity with so many large drives, you would be at risk of loosing it all if a drive dies and while rebuilding you get an unrecoverable error.

Re: ZFS Pool Expansion Options

Posted: 08 Dec 2013 05:10
by PCgeek215
Thanks for the reply Onichan,

Due to pricing constraints, I have decided to drop the additional drives down to 4 x 3TB (ie one parity drive). So If I have two vDevs with 4 drives in each with one of them being a parity drive I feel the protection should be adequate.

Thoughts?

Re: ZFS Pool Expansion Options

Posted: 09 Dec 2013 00:17
by Onichan
Well statistically you should be find, but most people say RAID5 is bad with drives over 1TB, see http://www.zdnet.com/blog/storage/why-r ... n-2009/162 and http://www.zdnet.com/blog/storage/why-r ... n-2019/805 though some say it isn't that bad http://www.high-rely.com/hr_66/blog/why ... -2009-not/. RAID isn't a backup anyways so you should have a backup of important data and it shouldn't be a major issue if you loose two drives anyways.