| From: | Fujii Masao <masao(dot)fujii(at)gmail(dot)com> |
|---|---|
| To: | Josh Berkus <josh(at)agliodbs(dot)com> |
| Cc: | PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Chronic performance issue with Replication Failover and FSM. |
| Date: | 2012-03-14 02:05:02 |
| Message-ID: | CAHGQGwECLh2tV1+MHapJg8+SAWErzvBbrFfen_F_6+PY7zACrA@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Wed, Mar 14, 2012 at 8:53 AM, Josh Berkus <josh(at)agliodbs(dot)com> wrote:
> All,
>
> I've discovered a built-in performance issue with replication failover
> at one site, which I couldn't find searching the archives. I don't
> really see what we can do to fix it, so I'm posting it here in case
> others might have clever ideas.
>
> 1. The Free Space Map is not replicated between servers.
>
> 2. Thus, when we fail over to a replica, it starts with a blank FSM.
>
> 3. I believe replica also starts with zero counters for autovacuum.
>
> 4. On a high-UPDATE workload, this means that the replica assumes tables
> have no free space until it starts to build a new FSM or autovacuum
> kicks in on some of the tables, much later on.
If it's really a high-UPDATE workload, wouldn't autovacuum start soon?
Regards,
--
Fujii Masao
NIPPON TELEGRAPH AND TELEPHONE CORPORATION
NTT Open Source Software Center
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