| From: | Andres Freund <andres(at)2ndquadrant(dot)com> |
|---|---|
| To: | Magnus Hagander <magnus(at)hagander(dot)net> |
| Cc: | Fujii Masao <masao(dot)fujii(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Subject: | Re: pg_basebackup failed to back up large file |
| Date: | 2014-06-03 16:30:31 |
| Message-ID: | 20140603163031.GR24145@awork2.anarazel.de |
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| Lists: | pgsql-hackers |
On 2014-06-03 18:23:07 +0200, Magnus Hagander wrote:
> On Jun 3, 2014 6:17 PM, "Andres Freund" <andres(at)2ndquadrant(dot)com> wrote:
> > PG's tar.c already uses the ustar format and the referenced extension is
> > an extension to ustar as far as I understand it. So at least tarballs
> > with files < 8GB would still continue to be readable with all currently
> > working implementations.
>
> Yeah, that is a clear advantage of that method. Didn't read up on pax
> format backwards compatibility, does it have some trick to achieve
> something similar?
It just introduces a new file type 'x' that's only used when extended
features are needed. That file type then contains the extended header.
So the normal ustar header is used for small files, and if more is
needed an *additional* extended header is added.
Check:
http://pubs.opengroup.org/onlinepubs/9699919799/utilities/pax.html#tag_20_92_13_01
Greetings,
Andres Freund
--
Andres Freund http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
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