Subject: Re: Distributing data over "spindles" even on AWS EBS, (followup to
 the work queue saga)
To: Gunther <raj@gusw.net>, <pgsql-performance@lists.postgresql.org>
References: <b49c6a04-caaf-a3d1-4f07-978558260cf8@gusw.net>
 <679375f7-bb61-6a66-e91a-4b5454f9223b@gusw.net>
From: Jeremy Schneider <schnjere@amazon.com>
Message-ID: <b2648191-36b1-9ef2-5833-24b1c8d1cd26@amazon.com>
Date: Thu, 14 Mar 2019 08:11:20 -0700
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On 3/14/19 07:53, Gunther wrote:
>  2. build a low level "spreading" scheme which is to take the partial
>     files 4653828 and 4653828.1, .2, _fsm, etc. and move each to another
>     device and then symlink it back to that directory (I come back to this!)
...
> To 2. I find that it would be a nice feature of PostgreSQL if we could
> just use symlinks and a symlink rule, for example, when PostgreSQL finds
> that 4653828 is in fact a symlink to /otherdisk/PG/16284/4653828, then
> it would
>
>  * by default also create  4653828.1 as a symlink and place the actual
>    data file on /otherdisk/PG/16284/4653828.1

How about if we could just specify multiple tablespaces for an object,
and then PostgreSQL would round-robin new segments across the presently
configured tablespaces?  This seems like a simple and elegant solution
to me.


>  4. maybe I can configure in AWS EBS to reserve more IOPS -- but why
>     would I pay for more IOPS if my cost is by volume size? I can just
>     make another volume? or does AWS play a similar trick on us with
>     IOPS being limited on some "credit" system???

Not credits, but if you're using gp2 volumes then pay close attention to
how burst balance works. A single large volume is the same price as two
striped volumes at half size -- but the striped volumes will have double
the burst speed and take twice as long to refill the burst balance.

-Jeremy

-- 
Jeremy Schneider
Database Engineer
Amazon Web Services