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Date:      Wed, 13 Apr 2016 11:15:50 -0400
From:      Paul Mather <freebsd-lists@gromit.dlib.vt.edu>
To:        freebsd-questions@freebsd.org
Cc:        luciano@vespaperitivo.it
Subject:   Re: ZFS with errors
Message-ID:  <6DF8015A-9976-4DDE-BC9B-236F97470A36@gromit.dlib.vt.edu>
In-Reply-To: <mailman.3530.1460559332.54431.freebsd-questions@freebsd.org>
References:  <mailman.3530.1460559332.54431.freebsd-questions@freebsd.org>

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Luciano,

> Date: Wed, 13 Apr 2016 16:22:51 +0200
> From: Luciano Mannucci <luciano@vespaperitivo.it>
> To: freebsd-questions@freebsd.org
> Subject: Re: ZFS with errors
> Message-ID: <3qlQxr34YhzRRqQ@baobab.bilink.it>
> Content-Type: text/plain; charset=3Diso-8859-1
>=20
> On Wed, 13 Apr 2016 15:56:20 +0200 (CEST)
> Trond Endrest?l <Trond.Endrestol@fagskolen.gjovik.no> wrote:
>=20
>> There's no redundancy in this pool, making it hard for ZFS to=20
>> automatically repair your files.
>>=20
>> Maybe you should destroy your pool and recreate it using a mirrored=20=

>> configuration. Maybe, mirror disks 1 & 2, and disks 3 & 4, e.g.
> They are of different sizes. I don't know if I can add redundancy
> without loosing the bits that exeed the smallest one...
> I'm a zfs newbie, just experimenting by now... :)
>=20
> Thanks anyway,
>=20
> Luciano.


The only way you can add redundancy to the type of pool you have (i.e., =
several drives concatenated together without any mirroring or raidz =
redundancy) is to set the "copies=3D..." property on datasets for which =
you want some redundancy:

     copies=3D1 | 2 | 3
         Controls the number of copies of data stored for this dataset. =
These
         copies are in addition to any redundancy provided by the pool, =
for
         example, mirroring or RAID-Z. The copies are stored on =
different
         disks, if possible. The space used by multiple copies is =
charged to
         the associated file and dataset, changing the used property and
         counting against quotas and reservations.

         Changing this property only affects newly-written data. =
Therefore,
         set this property at file system creation time by using the -o
         copies=3DN option.



Note the "Changing this property only affects newly-written data" part, =
though. You could also apply this selectively if you don't want to lose =
too much pool space, e.g., to impart some redundancy to files in your =
home directory but not to other areas where data loss can easily be =
remedied or isn't as much of a problem (/usr/src; /usr/ports; /usr/obj; =
etc.).

Cheers,

Paul.=



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