Raidz in FreeNAS eating more space than expected

Posted by swood on Server Fault See other posts from Server Fault or by swood
Published on 2012-06-15T12:50:44Z Indexed on 2012/11/16 11:04 UTC
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Filed under:

storage

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zfs

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freenas

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raidz

I just got 6 new 2TB drives, and added them to my FreeNAS box. I have only dealt with RAID1 previously, and each setup has given what I was expecting.

However, with the 6*2TB drives, I wanted to maximize the space available, so I went with raidz. But I seem to be missing space. I have 8.6TB available after the raidz was built. Maybe I did my math horribly wrong, but (N-1) x S(min) (where N=6 and S(min)=2TB) should result in 10TB. (I understand it would be more like 9.something)

Does raidz actually consume more then 1 drive worth of space? Or could their possibly be another problem? (All drives have been independently verified that 2TB of space is available)

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