On Mon, Jun 17, 2013 at 12:18 PM, Lonni J Friedman <netll...@gmail.com>wrote:
> On Sat, Jun 15, 2013 at 8:03 PM, Bruce Momjian <br...@momjian.us> wrote: > > On Fri, Jun 14, 2013 at 02:29:24PM -0700, Lonni J Friedman wrote: > >> Greetings, > >> I'm in the early stages of preparing to upgrade a production 9.2 > >> cluster to 9.3, by testing the beta of 9.3. All of my testing is > >> happening on RHEL6-x86_64 on a dedicated server with 128GB RAM and 2x > >> Intel Xeon E5-2670 CPUs, with all of $PGDATA residing on an 8 disk > >> RAID10 array. > >> > >> Currently, a full pg_basebackup of my data is approaching 800GB in > >> size (uncompressed), so this isn't a tiny, trivial database. > >> > >> I was curious about how much of a performance gain I'd get from > >> upgrading with the new -j option to pg_upgrade, so first I performed > >> the upgrade without it to get a baseline. The command I ran for the > >> upgrade is as follows: > >> time pg_upgrade -v -d /var/lib/pgsql/9.2/data -D > >> /var/lib/pgsql/9.3/data -b /usr/pgsql-9.2/bin -B /usr/pgsql-9.3/bin > >> > >> time reported the following afterward the upgrade had completed > successfully: > >> real 24m59.255s > >> user 0m17.069s > >> sys 15m25.153s > >> > >> > >> I then repeated the upgrade (after blowing away $PGDATA, and running > >> initdb again for 9.3), and re-ran pg_upgrade with the same command as > >> above, only with '-j4' appended to the end. Surprisingly, the > >> completion time was less than 30 seconds faster. I repeated a third > >> time with '-j8', and that was about the same completion time as with > >> '-j4'. I guess I could repeat with 'j2', but I'd be surprised if it > >> was dramatically faster when -j4 was only marginally so. It seems > >> like the parallelism of the -j option doesn't seem to be helping much > >> at all, in my case. > >> > >> Is this expected, or is it possible that there's a bug somewhere? Let > >> me know if I can provide any logs from the upgrade. > > > > The documentation states: > > > > The <option>--jobs</> option allows multiple CPU cores to be used > > for copying/linking of files and to dump and reload database schemas > > in parallel; a good place to start is the maximum of the number of > > CPU cores and tablespaces. This option can dramatically reduce the > > time to upgrade a multi-database server running on a multiprocessor > > machine. > > > > My guess is that you didn't have many tablespaces or databases, or the > > copy time overwhelmed the performance improvement of the parallelism. > > I am not surprised you didn't see a big win. Can you test --link > > mode? > > I only have 1 tablespace, although I have 9 databases. However, one > of the databases is about 95% of the total on-disk space, so that's > probably the explanation of why -j isn't helping me? > > That is probably why you DID had some improvement, although so little. > I don't have sufficient disk space to efficiently test --link mode, > unless there's some way to quickly roll back to the pre-upgrade > version of the database after a --link mode upgrade has completed > successfully that I'm not seeing? > > I didn't got it. AFAIK, in link mode it would take **less** space than normal mode, not the opposite. Am I wrong? Unless you want to keep a backup of the old cluster on the same machine, but even on that case you could take this backup compressed, although the overall time would be worst. Regards, -- Matheus de Oliveira Analista de Banco de Dados Dextra Sistemas - MPS.Br nível F! www.dextra.com.br/postgres
