2016-09-02 15:36 GMT+12:00 Venkata B Nagothi <nag1...@gmail.com>: > > On Fri, Sep 2, 2016 at 12:48 PM, Patrick B <patrickbake...@gmail.com> > wrote: > >> Hi guys, >> >> I'll be performing a migration on my production master database server, >> which is running PostgreSQL 9.2 atm, from SATA disks to SSD disks. >> I've got some questions about it, and it would be nice if u guys could >> share your experiences/thoughts: >> >> *SCENARIO:* >> >> I currently have one MASTER and two Streaming Replication Slaves >> servers... >> >> master01 >>> slave01 (Streaming replication + wal_files) >>> slave02 (Streaming replication + wal_files) >> >> >> ...Postgres is mounted on: /var/lib/pgsql/... The SSD disks will be >> installed only on my Master server, because my main problem is Writes and >> not reads. >> >> The new SSD volume will be mounted on /var/lib/pgsql2/ >> >> >> >> - The slave02 server will loose the streaming replication connection >> to the master, once slave01 becomes the new master a new timeline will be >> settled? Will slave02 be able to connect to the slave01 server for >> streaming replication? >> >> Yes, slave01 becomes new master with a new timeline id. Cascading > replication is supported in 9.2, but, the dependency on WAL archives is a > bit heavy. You need to ensure .history file is copied over to slave02. I > think, you have WAL archiving enabled, so, should be fine. >
hmmm.... is the .history files located into pg_xlog? I can't see none.... are they only generated when a new timeline id is created? If so, I think it will be fine as they're already being shipped to the slaves > > *MIGRATION OPTIONS:* >> >> *Migration Option 1:* *I know this option will work* >> >> >> 1. Mount the new volume */var/lib/pgsql2/ *on the master01 server >> 2. Turn slave01 into a master server >> 3. once I can confirm everything is working fine, I can go to step 4 >> 4. Stop postgres on the master01, start copying the DB using >> pg_basebackup from slave02 to master01 (Will have to edit postgres to >> use /var/lib/pgsql2/ instead /var/lib/pgsql - Is that possible? Or I'd >> have >> to create a symbolic link?) >> 5. Start postgres on master01 server and check if all goes well as >> streaming replication server (Will test it for days) >> 6. Turn master01 into a master server and I'll have to re-copy the DB >> into slave01 to make it a streaming replication server again >> >> @ Step 4, you can consider making master01 slave directly by building a > new recovery.conf file and copying over slave02's history file by doing > which, you can avoid re-build streaming replication from scratch. > When you "edit postgres", did you mean changing postgresql.conf ? if yes, > changing the parameter in postgresql.conf to use the new location should > not be a problem. > > @ Step 6, Once you turn master01 (new slave) back to master server, you > can consider making slave01 (new master) a slave again by copying over the > .history files and required WALs. You do not have to build replication from > scratch. > > *Migration Option 2:* *I don't know if this is possible - IS THIS >> POSSIBLE????* >> >> 1. Mount the new volume */var/lib/pgsql2/* on the master01 server >> 2. Stop postgres on the server (I won't stop postgres on the slave so >> the users will be able to use the server as read-only) >> 3. Copy the data from /var/lib/pgsql/ to /var/lib/pgsql2/ >> 4. Configure postgres to start using the new volume(/var/lib/pgsql2/) >> >> This looks pretty straight forward. The only issue would be that, users > will not be able to do writes. If you are bringing down master and starting > up again, it should not a problem, slaves should be able catch up again. > > What do you guys think? Is option possible? if so it would be much easier >> :) >> > > Well, both the options work based on your expectations, Application > requirements on downtime, SLAs etc. > > So is that really possible? Just copy the data between folders? if so, i'll probably chose option 2!!! Even that is 2.5TB I don't think the copy will take longer than 20 minutes... and I'd still be able to perform reads... I'll do some test to see if option 2 can be done :) Thanks !!! :D
