Chris Parsons <[email protected]> wrote on 04/12/2011 10:12:59
PM:
> On 13/04/2011 11:21 AM, Timothy J Massey wrote:
>> Remember, you have to get them to another machine, so ZFS or any
>> other snapshot by itself won't finish the job: you then need to copy
>> them somewhere else. This includes SAN based solutions (though in
>> that case, "somewhere else" might just be defined as a different
>> storage shelf...).
> Ah, but that is where ZFS still provides the solution. Getting the
> data somewhere else is as simple as:
> [root@solaris]$ zfs snapshot master/data@1
> [root@solaris]$ zfs send master/data@1 | zfs receive slave/data
>
> The slave server, will now have an identical copy of the master.
> (Make it readonly for now however)
But *very* likely not any more efficiently than using LVM, possibly with
parted.
> And the next time,
> [root@solaris]$ zfs snapshot master/data@2
> [root@solaris]$ zfs send -i master/data@1 master/data@2 | zfs
> receive slave/data
>
> You will have only sent the differences between this snapshot and
> the last across.
I reserve judgements until I actually see this done, but if it's done
using a log-based structure instead of a block- (or extent-) based
structure I can certainly see the benefits here.
> So unlike ext3 + snapshots, ZFS will allow you to efficiently
> transfer your pool to another server.
Yes, very interesting. Kind of like BackupPC itself, the first transfer
will not be terribly fast, but subsequent transfers could potentially be
much faster.
Has anyone actually done this in production with realistic amounts of data
(and data turnover) to see how it *actually* works? Remember, for
example, that in theory LVM snapshotting is also the greatest thing since
sliced bread, too, but in practice there are actual rough edges to be
aware of.
>> So, I stick by my 4 options, with one of them possibly slightly
renamed.
> You might have me by definition on this. However, I like to think of
> ZFS as significantly more capable than other snapshot techniques.
Sure, but it's still the exact same technique. I am fully willing to
accept that ZFS may offer facilities that make it a better choice than
LVM, but it's still the same principle. I would *really* like to see that
in action...
> However, it comes with the obvious downside of having to run
> Solaris.
Which for me, to date, has been a *real* downside. I've tried to give
both OpenSolaris and Nexenta a fair evaluation within the last 6 months,
but both were poor contenders, especially in hardware support: anything
beyond commodity hardware was a tough fit. (No, I have no real interest
in Sun hardware...)
That and I have too many scars from using Sun userspace utilities for too
long... :)
Timothy J. Massey
Out of the Box Solutions, Inc.
Creative IT Solutions Made Simple!
http://www.OutOfTheBoxSolutions.com
[email protected]
22108 Harper Ave.
St. Clair Shores, MI 48080
Office: (800)750-4OBS (4627)
Cell: (586)945-8796
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