(no subject)

[merc1984]

We're using a backups server to back up all machines in a LAN.  Four 2TB
disks are assembled in a BTRFS RAID array and mounted as /media/backups.
 Under this are subvolumes droog, hex, etc, and snapshots
droog_snap-{date1}, hex_snap-{date1}, etc.

Goal is to encrypt backups, but the concern is with snapshots.  Won't
piping rsync through encryption with GPG or somesuch, play havoc with
BTRFS snapshot accounting?

Is there any way to encrypt an array so it is inaccesible while
umounted?

I've already asked on the ecryptfs listserv and it resulted in mass
confusion.

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Re: Encryption

[merc1984]

So there is no way to have filesystem encryption, while keeping
snapshots?


On Fri, Dec 7, 2012, at 8:16, [2]merc1984@f-m.fm wrote:

> We're using a backups server to back up all machines in a LAN.  Four 2TB disks are assembled in a BTRFS RAID array and mounted as /media/backups.  Under this are subvolumes droog, hex, etc, and snapshots droog_snap-{date1}, hex_snap-{date1}, etc.

> Goal is to encrypt backups, but the concern is with snapshots.  Won't piping rsync through encryption with GPG or somesuch, play havoc with BTRFS snapshot accounting?

> Is there any way to encrypt an array so it is inaccesible while umounted?

> I've already asked on the ecryptfs listserv and it resulted in mass confusion.

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Re: Encryption

[Mitch Harder]

On Wed, Dec 12, 2012 at 11:12 AM,  <merc1984@f-m.fm> wrote:
>
> So there is no way to have filesystem encryption, while keeping
> snapshots?
>
>

I run btrfs on top of LUKS encryption on my laptop.  You should be
able to do the same.

You could then run rsync through ssh.  However, rsync will have no
knowledge of any blocks shared under subvolume snapshots.

Btrfs does not yet have internal encryption.

Re: Encryption

[merc1984]

On Wed, Dec 12, 2012, at 10:31, Mitch Harder wrote:
> I run btrfs on top of LUKS encryption on my laptop.  You should be able to do the same.
>
> You could then run rsync through ssh.  However, rsync will have no knowledge of any blocks shared under subvolume snapshots.
>
> Btrfs does not yet have internal encryption.

The FAQ says specifically to NOT run BTRFS with any kind of volume
encryption, so you're asking for trouble.

And clearly encryption is not possible if you need snapshots.

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Re: Encryption

[cwillu]

On Wed, Dec 12, 2012 at 12:38 PM,  <merc1984@f-m.fm> wrote:
>
> On Wed, Dec 12, 2012, at 10:31, Mitch Harder wrote:
>> I run btrfs on top of LUKS encryption on my laptop.  You should be able to do the same.
>>
>> You could then run rsync through ssh.  However, rsync will have no knowledge of any blocks shared under subvolume snapshots.
>>
>> Btrfs does not yet have internal encryption.

> The FAQ says specifically to NOT run BTRFS with any kind of volume
> encryption, so you're asking for trouble.

Sayeth the FAQ:

Does Btrfs work on top of dm-crypt?
This is deemed safe since 3.2 kernels. Corruption has been reported
before that, so you want a recent kernel. The reason was improper
passing of device barriers that are a requirement of the filesystem to
guarantee consistency.

> And clearly encryption is not possible if you need snapshots.

Snapshots don't come into this at all:  btrfs doesn't care where the
block devices it's on come from.  Things like dm-crypt show btrfs (or
whatever filesystem you put on it) a decrypted view of the device.

Re: Encryption

[merc1984]

On Wed, Dec 12, 2012, at 10:48, cwillu wrote:
> Sayeth the FAQ:

Oh pardon me, it's BTRFS RAID that's a no-go, which is just as critical
to me as I have a 4 disk 8TB array.
The FAQ goeth on to Say:
-----------------------------------------------------------
This pretty much forbids you to use btrfs' cool RAID features if you
need encryption. Using a RAID implementation on top of several encrypted
disks is much slower than using encryption on top of a RAID device. So
the RAID implementation must be on a lower layer than the encryption,
which is not possible using btrfs' RAID support.
 -----------------------------------------------------------

You saw that I need RAID above.  Were you just trying to criticize my
memory of the FAQ cwillu?


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Re: Encryption

[cwillu]

On Wed, Dec 12, 2012 at 2:06 PM,  <merc1984@f-m.fm> wrote:
> On Wed, Dec 12, 2012, at 10:48, cwillu wrote:
>> Sayeth the FAQ:
>
> Oh pardon me, it's BTRFS RAID that's a no-go, which is just as critical
> to me as I have a 4 disk 8TB array.
> The FAQ goeth on to Say:
> -----------------------------------------------------------
> This pretty much forbids you to use btrfs' cool RAID features if you
> need encryption. Using a RAID implementation on top of several encrypted
> disks is much slower than using encryption on top of a RAID device. So
> the RAID implementation must be on a lower layer than the encryption,
> which is not possible using btrfs' RAID support.
>  -----------------------------------------------------------
>
> You saw that I need RAID above.  Were you just trying to criticize my
> memory of the FAQ cwillu?

It's not asking for trouble, it's just asking for poor performance,
and I suspect even that will depend greatly on the workload.

Snapshots still have nothing to do with it:  you could have btrfs
(with snapshots) on dm-crypt on mdraid.  Btrfs would just lose the
ability to try alternate mirrors and similar; snapshots would still
work just fine.

Re: Encryption

[Sander]

merc1984@f-m.fm wrote (ao):
> Oh pardon me, it's BTRFS RAID that's a no-go, which is just as critical
> to me as I have a 4 disk 8TB array.
> The FAQ goeth on to Say:
> -----------------------------------------------------------
> This pretty much forbids you to use btrfs' cool RAID features if you
> need encryption.

Forbids? That is just plain wrong.

I have one btrfs filesystem on top of two encrypted devices. Works just
fine.

	Sander

Re: Encryption

[merc1984]

On Thu, Dec 13, 2012, at 1:17, Sander wrote:
Forbids? That is just plain wrong.
I have one btrfs filesystem on top of two encrypted devices. Works just
fine.

That's dynamite Sander.

But I am not going to contravene the instructions, then have problems,
only to come back here and have fingers wagged in my face telling me
this is all EXPERIMENTAL!

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Re: Encryption

[Hugo Mills]

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On Thu, Dec 13, 2012 at 09:23:05AM -0800, merc1984@f-m.fm wrote:
> 
> On Thu, Dec 13, 2012, at 1:17, Sander wrote:
> Forbids? That is just plain wrong.
> I have one btrfs filesystem on top of two encrypted devices. Works just
> fine.
> 
> That's dynamite Sander.
> 
> But I am not going to contravene the instructions, then have problems,
> only to come back here and have fingers wagged in my face telling me
> this is all EXPERIMENTAL!

   Well, I'm afraid that applies to the information on the wiki, too
-- that's also experimental, to a degree. The notes on the wiki about
behaviour of encryption layers weren't added by any of the core
developers. Nobody's published concrete tests *either* way yet, and
those comments are one person's opinion, as far as I'm aware (and note
that they don't actually quote sources, results, or even personal
experience).

   YMMV.

   Hugo.

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