Обсуждение: pg_update to a new machine?

The 2.8TB database must be moved to a new server in a new Data Center, and upgraded from 8.4.17 to 9.6.6

Will this work?

pg_upgrade       --old-datadir "CURSERVER://var/lib/pgsql/data"       --new-datadir "NEWSERVER://var/lib/pgsql/data"       --old-bindir "CURSERVER://usr/bin"       --new-bindir "NEWSERVER://usr/bin"

Or must I:
1. temporarily allocate 3TB of scratch space on the new server,
2. install 8.4 on the new server,
3. install 9.6.6 on the new server,
2. rsync CURSERVER://var/lib/pgsql/data to NEWSERVER://var/lib/pgsql/8.4/data, and then
3. pg_upgrade?

Are there better ways?  (The pipe from current DC to new DC will be 10Gbps.)

Thanks

Am 24.02.2018 um 04:57 schrieb Ron Johnson:
> The 2.8TB database must be moved to a new server in a new Data Center, 
> and upgraded from 8.4.17 to 9.6.6
>
> Will this work?
>
> pg_upgrade
>          --old-datadir "CURSERVER://var/lib/pgsql/data"
>          --new-datadir "NEWSERVER://var/lib/pgsql/data"
>          --old-bindir "CURSERVER://usr/bin"
>          --new-bindir "NEWSERVER://usr/bin"
> Or must I:
> 1. temporarily allocate 3TB of scratch space on the new server,
> 2. install 8.4 on the new server,
> 3. install 9.6.6 on the new server,
> 2. rsync CURSERVER://var/lib/pgsql/data to 
> NEWSERVER://var/lib/pgsql/8.4/data, and then
> 3. pg_upgrade?
>
> Are there better ways?  (The pipe from current DC to new DC will be 
> 10Gbps.)
>

it's a big step from 8.4 to 9.6... If you can do that with a downtime i 
would prefer dump & restore.
A solution without (big) downtime would be replication with slony or 
londiste.


Regards, Andreas

-- 
2ndQuadrant - The PostgreSQL Support Company.
www.2ndQuadrant.com

Greetings,

* Ron Johnson (ron.l.johnson@cox.net) wrote:
> The 2.8TB database must be moved to a new server in a new Data Center, and
> upgraded from 8.4.17 to 9.6.6
>
> Will this work?
>
> pg_upgrade
>         --old-datadir "CURSERVER://var/lib/pgsql/data"
>         --new-datadir "NEWSERVER://var/lib/pgsql/data"
>         --old-bindir "CURSERVER://usr/bin"
>         --new-bindir "NEWSERVER://usr/bin"

No, you can't specify hostnames to pg_upgrade.  You could possibly use
NFS or something else to be able to facilitate the above.

> Or must I:
> 1. temporarily allocate 3TB of scratch space on the new server,

If you use --link mode during pg_upgrade, you don't actually need to
allocate that scratch space on the new server.

> 2. install 8.4 on the new server,
> 3. install 9.6.6 on the new server,

For pg_upgrade, you do need both versions installed on the server you're
running pg_upgrade on, yes.  Please be sure to use the latest minor
version of each major version if you go that route.

> 2. rsync CURSERVER://var/lib/pgsql/data to
> NEWSERVER://var/lib/pgsql/8.4/data, and then

You can only perform this rsync with the database shut down, just to be
clear.  If you wanted to pull the data across with the database online,
you'd need to set up an archive_command and use a tool which works with
8.4 to perform an online backup (such as pgBackRest).

> 3. pg_upgrade?

If you perform an online backup and then capture all of the WAL using
archive_command, you could stand up a warm standby with 8.4 on the new
server which is replaying the WAL as it's generated on the primary by
specifying a restore_command on the new server.  Doing this, combined
with using pg_upgrade in --link mode, you would be able to perform the
flip from the old-server-on-8.4 to the new-server-with-9.6 in a
relatively short period of time (on the order of minutes-to-an-hour,
potentially).

> Are there better ways?  (The pipe from current DC to new DC will be 10Gbps.)

The above approach would work, but you wouldn't be able to enable
checksums on the new server, which is something I'd certainly recommend
doing if you're able to.  To get page-level checksums, you would need to
make sure you initdb the new server with them and then use the newer
pg_dump version to dump the 8.4 data out and then into the 9.6 server.
This could possibly be done as a pipe, but I'd probably find 1TB of
space somewhere and use parallel pg_dump to extract the data out and
into a compressed logical dump and then parallel pg_restore to pull it
into the new server.  This would also re-check all constraints in the
system and rebuild all indexes, but would naturally require more
downtime.

Thanks!

Stephen

Greetings,

* Ron Johnson (ron.l.johnson@cox.net) wrote:

The 2.8TB database must be moved to a new server in a new Data Center, and
upgraded from 8.4.17 to 9.6.6

Will this work?

pg_upgrade       --old-datadir "CURSERVER://var/lib/pgsql/data"       --new-datadir "NEWSERVER://var/lib/pgsql/data"       --old-bindir "CURSERVER://usr/bin"       --new-bindir "NEWSERVER://usr/bin"

No, you can't specify hostnames to pg_upgrade.  

I didn't think it would work, but it was worth an ask...

You could possibly use
NFS or something else to be able to facilitate the above.

Or must I:
1. temporarily allocate 3TB of scratch space on the new server,

If you use --link mode during pg_upgrade, you don't actually need to
allocate that scratch space on the new server.

I'll look into that.

2. install 8.4 on the new server,
3. install 9.6.6 on the new server,

For pg_upgrade, you do need both versions installed on the server you're
running pg_upgrade on, yes.  Please be sure to use the latest minor
version of each major version if you go that route.

2. rsync CURSERVER://var/lib/pgsql/data to
NEWSERVER://var/lib/pgsql/8.4/data, and then

You can only perform this rsync with the database shut down, just to be
clear.  If you wanted to pull the data across with the database online,
you'd need to set up an archive_command and use a tool which works with
8.4 to perform an online backup (such as pgBackRest).

To set up log shipping on 8.4, I do this, which works well:

select pg_start_backup('some_meaningful_tag');
nohup rsync -avz /var/lib/pgsql/data/* postgres@${DESTIP}:/var/lib/pgsql/data/ &
select pg_stop_backup();
p { margin-bottom: 0.1in; direction: ltr; line-height: 120%; text-align: left; }a:link { color: rgb(0, 0, 255); }
Would I, essentially (or in fact), have to set up log shipping from old to new?

3. pg_upgrade?

If you perform an online backup and then capture all of the WAL using
archive_command, you could stand up a warm standby with 8.4 on the new
server which is replaying the WAL as it's generated on the primary by
specifying a restore_command on the new server.

I guess that means "yes, set up log shipping"?

  Doing this, combined
with using pg_upgrade in --link mode, you would be able to perform the
flip from the old-server-on-8.4 to the new-server-with-9.6 in a
relatively short period of time (on the order of minutes-to-an-hour,
potentially).

Are there better ways?  (The pipe from current DC to new DC will be 10Gbps.)

The above approach would work, but you wouldn't be able to enable
checksums on the new server, which is something I'd certainly recommend
doing if you're able to.

We'll benchmark it.

  To get page-level checksums, you would need to
make sure you initdb the new server with them and then use the newer
pg_dump version to dump the 8.4 data out and then into the 9.6 server.
This could possibly be done as a pipe, but I'd probably find 1TB of
space somewhere and use parallel pg_dump

Is parallel pg_dump available on 8.4, or am I misinterpreting you?

 to extract the data out and
into a compressed logical dump and then parallel pg_restore to pull it
into the new server.  This would also re-check all constraints in the
system and rebuild all indexes, but would naturally require more
downtime.

Thanks!

Stephen

--
Angular momentum makes the world go 'round.

Greetings,

* Ron Johnson (ron.l.johnson@cox.net) wrote:
> On 02/24/2018 08:18 AM, Stephen Frost wrote:
> >* Ron Johnson (ron.l.johnson@cox.net) wrote:
> >>2. install 8.4 on the new server,
> >>3. install 9.6.6 on the new server,
> >For pg_upgrade, you do need both versions installed on the server you're
> >running pg_upgrade on, yes.  Please be sure to use the latest minor
> >version of each major version if you go that route.
> >
> >>2. rsync CURSERVER://var/lib/pgsql/data to
> >>NEWSERVER://var/lib/pgsql/8.4/data, and then
> >You can only perform this rsync with the database shut down, just to be
> >clear.  If you wanted to pull the data across with the database online,
> >you'd need to set up an archive_command and use a tool which works with
> >8.4 to perform an online backup (such as pgBackRest).
>
> To set up log shipping on 8.4, I do this, which works well:
>
> select pg_start_backup('some_meaningful_tag');
> nohup rsync -avz /var/lib/pgsql/data/* postgres@${DESTIP}:/var/lib/pgsql/data/ &
> select pg_stop_backup();

That's not log shipping, for log shipping you need to specify an
archive_command and actually capture all of the WAL generated, or, at a
minimum, the WAL generated between the start and stop backup calls.

Note that the above also doesn't do anything to verify that the data is
written out to the disk on the destination side.

> Would I, essentially (or in fact), have to set up log shipping from old to new?

You must capture the WAL generated between the start and stop backup for
a backup to be valid.  Beyond that, if you want the warm standby to
replay the changes made to the primary through WAL, you need to be
capturing the WAL generated on the primary using archive_command and
then specify a restore_command on the warm standby which will get the
WAL segments to be replayed.

> >>3. pg_upgrade?
> >If you perform an online backup and then capture all of the WAL using
> >archive_command, you could stand up a warm standby with 8.4 on the new
> >server which is replaying the WAL as it's generated on the primary by
> >specifying a restore_command on the new server.
>
> I guess that means "yes, set up log shipping"?

I'm not sure what you're asking here, but if you wish to minimize
downtime, then, yes, set up a warm standby which is being updated
through log shipping.

> >   Doing this, combined
> >with using pg_upgrade in --link mode, you would be able to perform the
> >flip from the old-server-on-8.4 to the new-server-with-9.6 in a
> >relatively short period of time (on the order of minutes-to-an-hour,
> >potentially).
>
> >>Are there better ways?  (The pipe from current DC to new DC will be 10Gbps.)
> >The above approach would work, but you wouldn't be able to enable
> >checksums on the new server, which is something I'd certainly recommend
> >doing if you're able to.
>
> We'll benchmark it.
>
> >   To get page-level checksums, you would need to
> >make sure you initdb the new server with them and then use the newer
> >pg_dump version to dump the 8.4 data out and then into the 9.6 server.
> >This could possibly be done as a pipe, but I'd probably find 1TB of
> >space somewhere and use parallel pg_dump
>
> Is parallel pg_dump available on 8.4, or am I misinterpreting you?

The pg_dump you'll be using is from the version you're upgrading *to*,
so it will support parallel jobs.  With an 8.4 server, you'll need to
stop all write traffic before running the pg_dump and you'll have to
specify '--no-synchronized-snapshots' as that's a feature which the 8.4
server doesn't support.

Thanks!

Stephen

On 02/24/2018 03:10 PM, Stephen Frost wrote:
[snip]
>> To set up log shipping on 8.4, I do this, which works well:
>>
>> select pg_start_backup('some_meaningful_tag');
>> nohup rsync -avz /var/lib/pgsql/data/* postgres@${DESTIP}:/var/lib/pgsql/data/ &
>> select pg_stop_backup();
> That's not log shipping, for log shipping you need to specify an
> archive_command and actually capture all of the WAL generated, or, at a
> minimum, the WAL generated between the start and stop backup calls.

That's steps #8, 9 and 10 (in our checklist) of setting up log shipping.  
Step #4 is configuring the archive_* statements in postgresql.conf.



-- 
Angular momentum makes the world go 'round.

Ron,

* Ron Johnson (ron.l.johnson@cox.net) wrote:
> On 02/24/2018 03:10 PM, Stephen Frost wrote:
> [snip]
> >>To set up log shipping on 8.4, I do this, which works well:
> >>
> >>select pg_start_backup('some_meaningful_tag');
> >>nohup rsync -avz /var/lib/pgsql/data/* postgres@${DESTIP}:/var/lib/pgsql/data/ &
> >>select pg_stop_backup();
> >That's not log shipping, for log shipping you need to specify an
> >archive_command and actually capture all of the WAL generated, or, at a
> >minimum, the WAL generated between the start and stop backup calls.
>
> That's steps #8, 9 and 10 (in our checklist) of setting up log shipping. 
> Step #4 is configuring the archive_* statements in postgresql.conf.

I would still recommend you use a tool developed specifically for taking
proper PG backups which validates that all WAL generated during a backup
is properly archived, such as pgBackRest, which also makes sure to sync
all the data out to persistent storage and can also operate in parallel
and perform incremental restores.

Thanks!

Stephen

On 02/24/2018 06:40 PM, Stephen Frost wrote:
> Ron,
>
> * Ron Johnson (ron.l.johnson@cox.net) wrote:
>> On 02/24/2018 03:10 PM, Stephen Frost wrote:
>> [snip]
>>>> To set up log shipping on 8.4, I do this, which works well:
>>>>
>>>> select pg_start_backup('some_meaningful_tag');
>>>> nohup rsync -avz /var/lib/pgsql/data/* postgres@${DESTIP}:/var/lib/pgsql/data/ &
>>>> select pg_stop_backup();
>>> That's not log shipping, for log shipping you need to specify an
>>> archive_command and actually capture all of the WAL generated, or, at a
>>> minimum, the WAL generated between the start and stop backup calls.
>> That's steps #8, 9 and 10 (in our checklist) of setting up log shipping.
>> Step #4 is configuring the archive_* statements in postgresql.conf.
> I would still recommend you use a tool developed specifically for taking
> proper PG backups which validates that all WAL generated during a backup
> is properly archived, such as pgBackRest, which also makes sure to sync
> all the data out to persistent storage and can also operate in parallel
> and perform incremental restores.

OK.  I'll try to get it installed.  (Lots of paperwork, etc.)


-- 
Angular momentum makes the world go 'round.