ZFS install on a partition

Ivailo Tanusheff Ivailo.Tanusheff at skrill.com
Sat May 18 07:26:17 UTC 2013


The overhead depends of the quantity of the changes you made since the oldest snapshot and the current data on the ZFS pool.
The snapshots keep only the differences between the live system and each other, 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 when you create/delete a snapshot, as the system should calculate the changes.

Best regards,
Ivailo Tanusheff

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

Le 18 mai 2013 à 06:49, kpneal at pobox.com a écrit :

> On Fri, May 17, 2013 at 08:03:30PM -0400, Paul Kraus wrote:
>> On May 17, 2013, at 6:24 PM, "bsd at todoo.biz" <bsd at todoo.biz> wrote:
>>> 3. Should I avoid using ZFS since my system is not well tuned and It would be asking for trouble to use ZFS in these conditions. 
>> 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 
>> detect the corrupt data and note it. If you had a mirror or other 
>> redundant device, ZFS would then read the data from the *other* copy 
>> and rewrite the bad block (or mark that physical block bad and use another).
> I believe the "copies=2" and "copies=3" option exists to enable ZFS to 
> self heal despite ZFS not being in charge of RAID. If ZFS only has a 
> single LUN to work with, but the copies=2 or more option is set, then 
> if ZFS detects an error it can still correct it.
> This option is a dataset option, is inheritable by child datasets, and 
> can be changed at any time affecting data written after the change. To 
> get the full benefit you'll therefore want to set the option before 
> 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. 

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

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

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