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Cc: freebsd-hackers@freebsd.org, xorquewasp@googlemail.com
Subject: Re: Request for opinions - gvinum or ccd?
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>    Disks, unlike software, sometimes fail. Using redundancy can help

modern SATA drives fail VERY often. about 30% of drives i bought recently 
failed in less than a year.

> both checksum on and copies > 1 on, and the latter isn't the
> default. It's probably better to let zpool provide the redundancy via
> a mirror or raid configuration than to let zfs do it anyway.

ZFS copies are far from what i consider useful.

for example you set copies=2. You write a file, and get 2 copies.

Then one disk with one copy fails, then you put another, do resilver but 
ZFS DOES NOT rebuild second copy.

You need to write a program that will just rewrite all files to make this.