| From: | Robert Schnabel <schnabelr(at)missouri(dot)edu> |
|---|---|
| To: | Scott Marlowe <scott(dot)marlowe(at)gmail(dot)com> |
| Cc: | Robert Haas <robertmhaas(at)gmail(dot)com>, cb <cb(at)mythtech(dot)net>, "pgsql-performance(at)postgresql(dot)org" <pgsql-performance(at)postgresql(dot)org> |
| Subject: | Re: Is Diskeeper Automatic Mode safe? |
| Date: | 2009-11-16 20:32:51 |
| Message-ID: | 4B01B6F3.6090100@missouri.edu |
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| Lists: | pgsql-performance |
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Scott Marlowe wrote:
<blockquote
cite="mid:dcc563d10911161212w3ac11a05l39b32a6d7b691fb9(at)mail(dot)gmail(dot)com"
type="cite">
<pre wrap="">On Mon, Nov 16, 2009 at 1:04 PM, Robert Schnabel <a class="moz-txt-link-rfc2396E" href="mailto:schnabelr(at)missouri(dot)edu"><schnabelr(at)missouri(dot)edu></a> wrote:
</pre>
<blockquote type="cite">
<pre wrap=""> So the short answer is yes, I have it running with
PostgreSQL and have not had any problems.
Have you unplugged the power cord a few times in the middle of heavy
write activity?
...Robert
Nope. Forgive my ignorance but isn't that what a UPS is for anyway? Along
with a BBU controller.
</pre>
</blockquote>
<pre wrap=""><!---->
BBU controller, yes. UPS, no. I've seen more than one multi-million
dollar hosting center go down from something as simple as a piece of
wire flying into a power conditioner, shorting it out, and feeding
back and blowing every single power conditioner and UPS AND the switch
that allowed the diesel to come into the loop. All failed. Every
machine lost power. One database server out of a few dozens came back
up. In fact there were a lot of different dbm systems running in that
center, and only the pg 7.2 version came back up unscathed.
Because someone insisted on pulling the plug out from the back a dozen
or so times to make sure it would do come back up. PG saved our
shorts and the asses they contain. Sad thing is I'm sure the other
servers COULD have come back up if they had been running proper BBUs
and hard drives that didn't lie about fsync, and an OS that enforced
fsync properly, at least for scsi, at the time.
Power supplies / UPSes fail far more often than one might think. And
a db that doesn't come back up afterwards is not to be placed into
production.
</pre>
</blockquote>
Ok, so you have sufficiently sparked my curiosity as to whether
Diskeeper will in any way cause Postgres to fail the power chord test.
Unfortunately I have some deadlines to meet so won't be able to test
this out until later in the week. I'm in the fortunate position that
the only person that uses my db is me myself and I so I can control
what and when it does work. I also have backup software running that
does complete drive imaging so I should be able to do this fairly
safely. Here is the plan...<br>
<br>
1) Shut down the Diskeeper service, run a query that is write heavy and
then pull the chord on the box. Wait a few minutes then plug it back
in and see if it recovers.<br>
2) Leave Diskeeper running and repeat the above...<br>
<br>
Comments/suggestions? If I'm going to do this I'd like to make sure I
do it correctly so it will be useful for the group.<br>
<br>
I'm using XP 64 bit, Adaptec 52445 + BBU, I have two external drive
enclosures (8 each) plus the 8 in the box, pg 8.4.0<br>
<br>
Bob<br>
<br>
<br>
<br>
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