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From Robert Newson <robert.new...@gmail.com>
Subject Re: Incremental backups
Date Thu, 25 Nov 2010 13:55:41 GMT
"Maybe theoretically, I could make a roll back on any db, simply by chopping
off some bytes  from the end?"

Yup, you can do that. CouchDB will seek backward from the end of the
file for the latest db header and then carry on as normal.

The real question is why you would want to? This scheme also prevents
you from ever compacting, as this will remove the previous revisions
of your documents.

B.

On Thu, Nov 25, 2010 at 1:48 PM, afters <afters.mail@gmail.com> wrote:
> This way I could recover from failure, but I couldn't roll back to a
> previous point in time as I could with incremental backups.
>
> Maybe theoretically, I could make a roll back on any db, simply by chopping
> off some bytes  from the end?
>
> On 25 November 2010 14:38, Robert Newson <robert.newson@gmail.com> wrote:
>
>> The best way to backup is via replication, in my opinion. You can do
>> this continuously so your backup will be very close to the original.
>>
>> On Thu, Nov 25, 2010 at 12:36 PM, Robert Newson <robert.newson@gmail.com>
>> wrote:
>> > "but are ALL db changes indeed append only?"
>> >
>> > Yes. the file is opened with O_APPEND, we *can't* write anywhere but
>> > the end of the file.
>> >
>> > Earlier versions of couchdb would update the header (the first 4k of
>> > the file) but that is no longer the case. It's strictly append only.
>> > Any truncation of the .couch file will yield a consistent database
>> > (obviously missing the most recent changes".
>> >
>> > B.
>> >
>> >
>> > On Thu, Nov 25, 2010 at 11:41 AM, afters <afters.mail@gmail.com> wrote:
>> >> I guess I'm not sure as to what's going on with the file as it is being
>> >> copied and changed at the same time. I assume that the file must be
>> >> append-only for this to work, but are ALL db changes indeed append only?
>> I
>> >> remember reading that updating a tree-node also updates all its
>> ancestors
>> >> (to track latest seq) and I wonder if those changes are also append
>> only.
>> >>
>> >> On 25 November 2010 13:21, Robert Newson <robert.newson@gmail.com>
>> wrote:
>> >>
>> >>> just copy the file, there's no need to stop couchdb. Replication would
>> >>> be another way, of course.
>> >>>
>> >>> On Thu, Nov 25, 2010 at 11:16 AM, afters <afters.mail@gmail.com>
>> wrote:
>> >>> > hi folks,
>> >>> >
>> >>> > As I'm about to implement it myself, I'm curious to know how people
>> >>> handle
>> >>> > incremental backups for their DB's.
>> >>> >
>> >>> > The straight-forward way, as I see it, is to shutdown couch and
use a
>> >>> tool
>> >>> > like rsync or duplicity to backup db files. It should do the job
>> well,
>> >>> and
>> >>> > as an added bonus, it could also be used to backup views.
>> >>> >
>> >>> > Does anyone know if a similar backup could be done while the couch
is
>> >>> still
>> >>> > on (and the db is being updated)?
>> >>> >
>> >>> > Does anyone do incremental backups using replication?
>> >>> >
>> >>> >  a.
>> >>> >
>> >>>
>> >>
>> >
>>
>

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