Thread: Doubt about pg_upgrade with link mode

Hi,

I'm trying to upgrade a PG 9.1 cluster to a 9.3 one.
I'm trying to use --link to do it in link mode since I don't have much
disk space for the migration.

I'm not totally sure that the --link parameter is being honored. I
can't see any mention about link mode in the migration logs and the
new cluster takes too much space.

I would like to understand how link mode really works. What does it
link and what does it copy. Unfortunately I didn't find information
about that. Any link that provides more info would be appreciated.

I've compare inodes from base files in the old data directory and the
new one and they are different.

copying "/9.1/base/18976/74003" to "/9.3/base/16416/73829"

$ stat /mnt/pg_data/base/18976/74001 --printf=%i
12454860

$ stat /mnt/pg_data-9.3/base/16416/73829 --printf=%i
10488427

It doesn't seem to be a hard link. Should it?

Ok, sorry for the noise. I had a error in my upgrade script, and it
was not being really honored.
Now it worked.

However it still would be great being able to read some article or
documentation that details a little bit information about the link
mode.

Cheers

2014-05-26 16:37 GMT+02:00 Luis <luisico@gmail.com>:
> Hi,
>
> I'm trying to upgrade a PG 9.1 cluster to a 9.3 one.
> I'm trying to use --link to do it in link mode since I don't have much
> disk space for the migration.
>
> I'm not totally sure that the --link parameter is being honored. I
> can't see any mention about link mode in the migration logs and the
> new cluster takes too much space.
>
> I would like to understand how link mode really works. What does it
> link and what does it copy. Unfortunately I didn't find information
> about that. Any link that provides more info would be appreciated.
>
> I've compare inodes from base files in the old data directory and the
> new one and they are different.
>
> copying "/9.1/base/18976/74003" to "/9.3/base/16416/73829"
>
> $ stat /mnt/pg_data/base/18976/74001 --printf=%i
> 12454860
>
> $ stat /mnt/pg_data-9.3/base/16416/73829 --printf=%i
> 10488427
>
> It doesn't seem to be a hard link. Should it?

On Mon, May 26, 2014 at 04:45:55PM +0200, Luis wrote:
> Ok, sorry for the noise. I had a error in my upgrade script, and it
> was not being really honored.
> Now it worked.
>
> However it still would be great being able to read some article or
> documentation that details a little bit information about the link
> mode.

There is a pg_upgrade presentation here:

    http://momjian.us/main/presentations/features.html#pg_upgrade

Link mode uses hard links, as documented --- not sure what more I can
say on that.

--
  Bruce Momjian  <bruce@momjian.us>        http://momjian.us
  EnterpriseDB                             http://enterprisedb.com

  + Everyone has their own god. +