EBS snapshot backups from a FreeBSD zfs file system: zpool freeze?

[Jeremy Chadwick]

On Wed, Jul 03, 2013 at 02:08:13PM +1200, Berend de Boer wrote:
> >>>>> "Adam" == Adam Vande More <amvandemore at gmail.com> writes:
> 
>     Adam> What is wrong with a simple ZFS snapshot and running the
>     Adam> backup against it? Â I assume that's how most of us are doing
>     Adam> it.
> 
> For starters, I suppose very few people are using FreeBSD on AWS, so
> "most of us" don't have a choice :-)
> 
> But this might simply be my understanding: what if I want to use the
> EBS snapshot of the 5 disks I've taken and attach them to another
> machine, and mount it?
>
> But perhaps you don't know what an EBS snapshot is? It's not a backup
> of your file system, it's a hardware-based backup of a disk at a
> single point in time.
>
> I.e. with EBS I can take a snapshot of 5 1TB, create new disks from
> it, and attach it to another machine. In SECONDS.

Okay, I think I understand what you're asking.  Please correct me:

It sounds to me like the Linux OS images on AWS have utilities or the
capability to create EBS images that are snapshots of the "virtual
disks" that make up the AWS system, and that you can transfer these
to another Linux AWS machine and mount the EBS images, and that this is
being done within Linux itself.

Correct?

If so -- then what you're wanting to ask is: "does FreeBSD have support
for EBS images?"  (Meaning this has nothing to do with ZFS)  I get the
impression an EBS image is a proprietary Amazon thing, so you would need
to ask Amazon if they have the same utilities for FreeBSD, or ask the
individual(s) responsible for the FreeBSD AWS images if there are such
tools.  Again: nothing to do with ZFS.

The confusion for me lies in this statement (previous mail):

>>> On Linux' file systems I can freeze a file system, start the backup of
>>> all disks, and unfreeze.

You used the word "file system" here, not "disk".  Yet you then say:

> I'm not looking for a way to take a ZFS snapshot, stream that to S3
> for hours, and stream it back and write to another disk for hours.

Except ZFS is a filesystem, yet above you just said "On Linux I can
freeze a filesystem..."

Understand my confusion now?

> But in case I didn't get you: could you please let me know if your
> approach would allow me to take a consistent backup of my disks and
> mount them on another server or use them for recovery purposes?

ZFS snapshots will let you take a snapshot of a pool/filesystem
(including incremental, if needed).  You can send ZFS snapshots to
another system for use using "zfs send" and "zfs recv".

You can use ZFS snapshots for almost-bare-metal recovery depending on
how you set up your system, but it does not do recovery of things like
boot blocks/bootloaders or other nuances.  You would have to do those on
your own (set up the boot blocks, etc.), or do so at a different layer.

For example, referring to virtualisation/hypervisors: it is possible to
take a "snapshot of a disk used by a VM", and then take that snapshot
and move it to another machine where its added (as a new disk) + seen by
the OS as a new disk and can be used.

And that has nothing to do with ZFS -- that has to do with the VM
software and/or HV software.  *Sometimes* OS vendors actually have
utilities (running within the guest itself) that can do these tasks,
hence my paragraph above starting out with "If so --".

-- 
| Jeremy Chadwick                                   jdc at koitsu.org |
| UNIX Systems Administrator                http://jdc.koitsu.org/ |
| Making life hard for others since 1977.             PGP 4BD6C0CB |