Re: rsync and streaming replication

Sorry to be so long to answer :-(


2011/11/14 Scott Ribe <scott_ribe@elevated-dev.com>

    - How large is the db? By which I mean how much disk space does the data directory occupy?
20 GB

    - What's the bandwidth of the network connection to the distant slave?
during rsync, I see narly 125Mbits/sec

    - What's the CPU & disk on each end?
disk : 6 * 146GB 15Krpm RAID10
CPU :  16 cores Xeon(R) CPU  L5630  @ 2.13GHz   cache size      : 12288 KB

Only Postgres is running on my servers (no HTTP server, nothing else, ...). CPU usage is very low.

This afternoon, I have again sent some updates requests, which were replicated to the sslaves.
 :
- I am looking modification of modification dates and checksums of 2 tables among my 6000 tables :
For each file, the checksum is the same on all the slaves, but different from the checksum of the master.
For each file, the modification time is different on each node. (see below)

So if I want to promote one slave as the master, it will not need to copy data from the new master to the previous slaves with rsync, but it will copy all the files from the new master to the old master (which is now a slave).

I shall try tomorrow topromote again a slave, and I shall rsync withh --checksum.
I don't think that it is -a is very useful withh --checksum (no need to preserve modification times). Do you agree ?

 

On the master :
postgres@master-db01:/var/opt/hosting/db/profiles/bench/PG_9.0_201008051/29797$ ls -l  107867807
-rw------- 1 postgres postgres 5914624 Nov 15 14:31 107867807
postgres@master-db01:/var/opt/hosting/db/profiles/bench/PG_9.0_201008051/29797$ md5sum 107867807
23c28c6432c073d370e7e9624fd04e3b  107867807

postgres@master-db01:/var/opt/hosting/db/profiles/bench/PG_9.0_201008051/29797$ ls -l  107867867
-rw------- 1 postgres postgres 5996544 Nov 15 14:31 107867867
postgres@master-db01:/var/opt/hosting/db/profiles/bench/PG_9.0_201008051/29797$ md5sum 107867867
1f3398e18e22bfeb31ca2db82d8517f2  107867867
postgres@master-db01:/var/opt/hosting/db/profiles/bench/PG_9.0_201008051/29797$


On slave 1 :
postgres@master-db01:/var/opt/hosting/db/profiles/bench/PG_9.0_201008051/29797$ ls -l  107867807
-rw------- 1 postgres postgres 5914624 Nov 15 14:16 107867807
postgres@master-db01:/var/opt/hosting/db/profiles/bench/PG_9.0_201008051/29797$ md5sum 107867807
f79d93ca00ac400f709a028c597ca4ab  107867807
postgres@master-db01:/var/opt/hosting/db/profiles/bench/PG_9.0_201008051/29797$
postgres@master-db01:/var/opt/hosting/db/profiles/bench/PG_9.0_201008051/29797$ ls -l  107867867
-rw------- 1 postgres postgres 5996544 Nov 15 14:18 107867867
postgres@master-db01:/var/opt/hosting/db/profiles/bench/PG_9.0_201008051/29797$ md5sum 107867867
3d5534f855168378f5cb2e30d622c0aa  107867867


On slave 2 :
postgres@slave-db01:/var/opt/hosting/db/profiles/bench/PG_9.0_201008051/29797$ ls -l  107867807
-rw------- 1 postgres postgres 5914624 Nov 15 14:24 107867807
postgres@slave-db01:/var/opt/hosting/db/profiles/bench/PG_9.0_201008051/29797$ md5sum 107867807
f79d93ca00ac400f709a028c597ca4ab  107867807
postgres@slave-db01:/var/opt/hosting/db/profiles/bench/PG_9.0_201008051/29797$
postgres@slave-db01:/var/opt/hosting/db/profiles/bench/PG_9.0_201008051/29797$ ls -l  107867867
-rw------- 1 postgres postgres 5996544 Nov 15 14:25 107867867
postgres@slave-db01:/var/opt/hosting/db/profiles/bench/PG_9.0_201008051/29797$ md5sum 107867867
3d5534f855168378f5cb2e30d622c0aa  107867867



On slave 3 :
postgres@slave-db01:/var/opt/hosting/db/profiles/bench/PG_9.0_201008051/29797$ ls -l  107867807
-rw------- 1 postgres postgres 5914624 Nov 15 14:16 107867807
postgres@slave-db01:/var/opt/hosting/db/profiles/bench/PG_9.0_201008051/29797$ md5sum 107867807
f79d93ca00ac400f709a028c597ca4ab  107867807
postgres@slave-db01:/var/opt/hosting/db/profiles/bench/PG_9.0_201008051/29797$
postgres@slave-db01:/var/opt/hosting/db/profiles/bench/PG_9.0_201008051/29797$ ls -l  107867867
-rw------- 1 postgres postgres 5996544 Nov 15 14:18 107867867
postgres@slave-db01:/var/opt/hosting/db/profiles/bench/PG_9.0_201008051/29797$ md5sum 107867867
3d5534f855168378f5cb2e30d622c0aa  107867867
postgres@slave-db01:/var/opt/hosting/db/profiles/bench/PG_9.0_201008051/29797$
postgres@slave-db01:/var/opt/hosting/db/profiles/bench/PG_9.0_201008051/29797$

Jal