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Date:      Sat, 18 May 2013 07:26:01 +0000
From:      Ivailo Tanusheff <Ivailo.Tanusheff@skrill.com>
To:        "bsd@todoo.biz" <bsd@todoo.biz>, Liste FreeBSD <freebsd-questions@freebsd.org>
Subject:   RE: ZFS install on a partition
Message-ID:  <5cafe18bb81847e8b749f4b50081b07e@DB3PR07MB059.eurprd07.prod.outlook.com>
In-Reply-To: <511AEFEF-7CE6-4E48-916C-81FAF8F9DEED@todoo.biz>
References:  <F744BBF1-D98C-47BF-9546-14D1A9CB3733@todoo.biz> <5FB78660-EDA4-40DB-8A0D-B0DE23A0FB6C@kraus-haus.org> <20130518044900.GA30652@neutralgood.org> <511AEFEF-7CE6-4E48-916C-81FAF8F9DEED@todoo.biz>

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Hi,

The overhead depends of the quantity of the changes you made since the olde=
st snapshot and the current data on the ZFS pool.
The snapshots keep only the differences between the live system and each ot=
her, so if you have made 10GB changes over the last 7 days and your oldest =
snapshot is 7 days old - then the overhead will be a little more than 10GB =
(because of the system info) :)
So this is very efficient way to make the things run.

Just keep in mind that having a lot of snapshots can decrease performance w=
hen you create/delete a snapshot, as the system should calculate the change=
s.

Best regards,
Ivailo Tanusheff

-----Original Message-----
From: owner-freebsd-questions@freebsd.org [mailto:owner-freebsd-questions@f=
reebsd.org] On Behalf Of bsd@todoo.biz
Sent: Saturday, May 18, 2013 8:33 AM
To: Liste FreeBSD
Subject: Re: ZFS install on a partition


Le 18 mai 2013 =E0 06:49, kpneal@pobox.com a =E9crit :

> On Fri, May 17, 2013 at 08:03:30PM -0400, Paul Kraus wrote:
>> On May 17, 2013, at 6:24 PM, "bsd@todoo.biz" <bsd@todoo.biz> wrote:
>>> 3. Should I avoid using ZFS since my system is not well tuned and It wo=
uld be asking for trouble to use ZFS in these conditions.=20
>>=20
>> No. One of the biggest benefits of ZFS is the end to end data integrity.
>> IF there is a silent fault in the HW RAID (it happens), ZFS will=20
>> detect the corrupt data and note it. If you had a mirror or other=20
>> redundant device, ZFS would then read the data from the *other* copy=20
>> and rewrite the bad block (or mark that physical block bad and use anoth=
er).
>=20
> I believe the "copies=3D2" and "copies=3D3" option exists to enable ZFS t=
o=20
> self heal despite ZFS not being in charge of RAID. If ZFS only has a=20
> single LUN to work with, but the copies=3D2 or more option is set, then=20
> if ZFS detects an error it can still correct it.
>=20
> This option is a dataset option, is inheritable by child datasets, and=20
> can be changed at any time affecting data written after the change. To=20
> get the full benefit you'll therefore want to set the option before=20
> putting data into the relevant dataset.

Ok, good to know.
I planned to setup a consistent Snapshot policy and remote backup using zfs=
 send / receive That should be enough for me.=20

Is the overhead of this setup equal to double size used on disk ?=20


>=20
> --=20
> Kevin P. Neal                                http://www.pobox.com/~kpn/
>=20
> "Nonbelievers found it difficult to defend their position in \=20
>    the presense of a working computer." -- a DEC Jensen paper

________________________________________________
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=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=
=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF
BSD - BSD - BSD - BSD - BSD - BSD - BSD - BSD - ___________________________=
_____________________
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=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=
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PGP ID --> 0x1BA3C2FD

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