Re: Online base backup from the hot-standby

2011/5/31 Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>:
> On 31.05.2011 07:46, Jun Ishiduka wrote:
>>> I don't much like that approach. The standby would need to be able to
>>> write the backup history file to the archive at the end of backup, and
>>> we'd have to reintroduce the code to fetch it from archive and, when
>>> streaming, from the master. At the moment, the archiver doesn't even run
>>> in the standby.
>>
>> Please teach the reason for "The standby would need to be able to write
>> the backup history file to the archive at the end of backup" .
>> (I'd like to know why "to only pg_xlog" is wrong .)
>
> If the backup history file is not archived, the postgres process won't
> find it when you try to restore from the base backup. The new server has
> no access to the standby's pg_xlog directory.

Right. If we take a base backup from the standby by not using pg_basebackup,
since there is no way to share the backup history file from the standby to new
server, an idea like you suggested would be required.

OTOH, if we use pg_basebackup, I think that it makes sense that pg_basebackup
transfers the backup history file from the standby to new server, puts
it in the base
backup (pg_xlog?), and new server reads it from the base backup but not the
archive.

Regards,

--
Fujii Masao
NIPPON TELEGRAPH AND TELEPHONE CORPORATION
NTT Open Source Software Center