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Re: 8192 BLCKSZ ?

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: pgsql-hackers(at)postgresql(dot)org
Subject: Re: 8192 BLCKSZ ?
Date: 2000-11-28 21:24:34
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-hackers
Nathan Myers <ncm(at)zembu(dot)com> writes:
> In the event of a power outage, the drive will stop writing in
> mid-sector.

Really?  Any competent drive firmware designer would've made sure that
can't happen.  The drive has to detect power loss well before it
actually loses control of its actuators, because it's got to move
the heads to the safe landing zone.  If it checks for power loss and
starts that shutdown process between sector writes, never in the middle
of one, voila: atomic writes.

Of course, there's still no guarantee if you get a hardware failure
or sector write failure (recovery from the write failure might well
take longer than the drive has got).  But guarding against a plain
power-failure scenario is actually simpler than doing it the wrong

But, as you say, customary page sizes are bigger than a sector, so
this is all moot for our purposes anyway :-(

			regards, tom lane

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