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Date:      Thu, 6 Jan 2011 10:20:00 +0100
From:      Damien Fleuriot <ml@my.gd>
To:        Artem Belevich <fbsdlist@src.cx>
Cc:        "freebsd-stable@freebsd.org" <freebsd-stable@freebsd.org>, Chris Forgeron <cforgeron@acsi.ca>
Subject:   Re: ZFS - moving from a zraid1 to zraid2 pool with 1.5tb disks
Message-ID:  <CC37553B-EE13-4B5B-AC87-80D0ECC1A2B3@my.gd>
In-Reply-To: <AANLkTimezasVY%2BMJjWn2T9sBGQV-JrNmYqRwv_gPYPJP@mail.gmail.com>
References:  <4D1C6F90.3080206@my.gd> <ifsia5$5ub$2@dough.gmane.org> <4D21E679.80002@my.gd> <84882169-0461-480F-8B4C-58E794BCC8E6@my.gd> <BEBC15BA440AB24484C067A3A9D38D7E0149F32D13E3@server7.acsi.ca> <488AE93A-97B9-4F01-AD0A-0098E4B329C3@my.gd> <AANLkTimezasVY%2BMJjWn2T9sBGQV-JrNmYqRwv_gPYPJP@mail.gmail.com>

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You both make good points, thanks for the feedback :)

I am more concerned about data protection than performance, so I suppose rai=
dz2 is the best choice I have with such a small scale setup.

Now the question that remains is wether or not to use parts of the OS's ssd f=
or zil, cache, or both ?

---
Fleuriot Damien

On 5 Jan 2011, at 23:12, Artem Belevich <fbsdlist@src.cx> wrote:

> On Wed, Jan 5, 2011 at 1:55 PM, Damien Fleuriot <ml@my.gd> wrote:
>> Well actually...
>>=20
>> raidz2:
>> - 7x 1.5 tb =3D 10.5tb
>> - 2 parity drives
>>=20
>> raidz1:
>> - 3x 1.5 tb =3D 4.5 tb
>> - 4x 1.5 tb =3D 6 tb , total 10.5tb
>> - 2 parity drives in split thus different raidz1 arrays
>>=20
>> So really, in both cases 2 different parity drives and same storage...
>=20
> In second case you get better performance, but lose some data
> protection. It's still raidz1 and you can't guarantee functionality in
> all cases of two drives failing. If two drives fail in the same vdev,
> your entire pool will be gone.  Granted, it's better than single-vdev
> raidz1, but it's *not* as good as raidz2.
>=20
> --Artem



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