Re: pg_dump -Z6 (the default) can be pretty slow

On 10/18/23 17:37, Scott Ribe wrote:
> If you can use the directory format, then you can use multiple jobs to really speed up compressed dump (and restore).

It didn't occur to me to mention that I used it.  Do people really still not
use -Fd?

> Also, I'd suggest trying a run with lz4 compression--lz4 is particularly good at not slowing down when it encounters already-compressed data. Doesn't give really high compression ratios, but since you're already at -Z3, might be worth comparing.

I'm still using 9.6, so that feature isn't available yet.  When I get the Pg
15 VMs stood up (Pg15 binaries are not available for RHEL 6), I'm definitely
going to try that.

> (Personally, I stay away from zstd, as I've seen it create malformed backups because the encoder crashes with out-of-memory.)
>
> --
> Scott Ribe
> scott_ribe(at)elevated-dev(dot)com
> https://www.linkedin.com/in/scottribe/
>
>
>
>> On Oct 18, 2023, at 4:30 PM, Ron <ronljohnsonjr(at)gmail(dot)com> wrote:
>>
>> In preparation for moving from 9.6 to something supported, I ran a pg_dump/pg_restore test (since the migrated databases will be on new servers, and we purge off old partitions and add new partitions, pg_upgrade and logical replication are off the table).
>>
>> (The servers are VMs on ESX hosts, and on the same subnet.)
>>
>> Our databases are chock full of bytea fields holding compressed images. pg_dump -Fd -Z6 took 25 minutes, and 5.5GB disk space. (remember, it's a test!), while pg_dump -Fd -Z0 only took 90 seconds, but consumed 15GB.
>>
>> This isn't really surprising to anyone who's ever tried to gzip a jpg file...
>>
>> Quite the speed increase if you can swallow the increased disk usage.
>>
>> pg_dump -Z3 did the best: only 8.5 minutes, while using just 5.8GB disk space.
>>
>> --
>> Born in Arizona, moved to Babylonia.
>>
>>

--
Born in Arizona, moved to Babylonia.