[kwlug-disc] Filesystems for backups

[bob+kwlug at softscape.ca]

To piggy-pack onto this somewhat with my thoughts and experiences with BTRFS,

Totally agree with the "RAID 1" setup of BTRFS. The other RAID levels had serious design (or coding?) flaws in them and the developers announced that people should STOP using them for production (or anything you cared about). So that means you are down to 50% usable capacity if you do this. I'm not sure what the current status of this is, but I have not come across anything saying RAID5/6 was ready to consider again.

Now, my playing with BTRFS has been only that but the theoretical part that appealed to me the most was that you can add and remove disks (of whatever size) at will. You just rebalance the filesystem and it automagically incorporates or removes the changed disk while preserving the RAID1-ness of the data. This really appeals to me for the home lab which has a dog's breakfast of hard drives available at any given time.

It does have block check summing capabilities (like ZFS) as far as I understand, and I absolutely love the ability to use the --reflink option on cp to create COW files. There are many creative uses of that (eg: full copies of an encrypted Mac IMG file where the only disk space used is the delta from the last backup. Use that with 'rsync --inplace' and this is quick and efficient).

I think ZFS has better mindshare in the community but I get claustrophobic when I think about changing drive configurations that involve complete copies being made. Having said that though, I've never done any serious work with BTRFS but the theory of its capabilities in that regard really appeal to me. If I was doing it, I'd use ZFS for really important data. If it was a backup server in a proper 2 or 3 copy architecture, I likely would give BTRFS serious consideration, notwithstanding the 50% usable space hit on RAID1.

My $0.02

BB


> -----Original Message-----
> From: kwlug-disc <kwlug-disc-bounces at kwlug.org> On Behalf Of opengeometry-
> -- via kwlug-disc
> Sent: August 7, 2019 10:47 PM
> To: KWLUG discussion <kwlug-disc at kwlug.org>
> Cc: opengeometry at yahoo.ca
> Subject: Re: [kwlug-disc] Filesystems for backups
> 
> 1.  I chose btrfs mainly because I didn't want to throw away Samsung
>     1TBs that I paid good money for.  (Yes, they're still going, while
>     WDs and Seagates have all been replaced.)  I use "raid 1" option
>     which means, in btrfs context, a block is copied on some other
>     device.  Harddisks need not be all same size, so it's not raid 1 in
>     mdadm sense.
> 
> 2.  I take daily, weekly, and monthly snapshots of backup.  I used to
>     take series of daily snapshots, but settled on daily, weekly, and
>     monthly cron jobs from /etc/cron.*.  Main disadvantage is that if
>     1st of month is also Sunday, then you will end up with all the
>     snaphots being the same.
> 
> 3.  "Scrubbing" takes long long time.
> 
> 4.  I don't think you have to prepare the disk before adding to btrfs
>     setup.  (It's been long time since I added one.)  But, for the first
>     system, you would do "mkfs.btrfs" like any other filesystem.
> 
> 5.  Performance wise, it's ok for backup.
> --
> William Park <opengeometry at yahoo.ca>
> 
> On Wed, Aug 07, 2019 at 09:27:13PM -0400, Paul Nijjar wrote:
> >
> > Tell me more. Do you configure the disks in btrfs in any particular
> > way? How do you feel about this solution?
> >
> > - Paul
> >
> > On Wed, Aug 07, 2019 at 11:26:34PM +0000, William Park via kwlug-disc
> wrote:
> > > I'm using btrfs on leftover hard disks as backup.--William
> 
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