Message-Id: <5.2.1.1.1.20060514162127.027ea4f8@localhost>
Date: Sun, 14 May 2006 16:31:00 +0800
To: Tom Lane <tgl@sss.pgh.pa.us>,
	Scott Ribe <scott_ribe@killerbytes.com>
From: Lincoln Yeoh <lyeoh@pop.jaring.my>
Subject: Re: [PERFORM] Arguments Pro/Contra Software Raid 
Cc: "Jim C. Nasby" <jnasby@pervasive.com>,
	Bruce Momjian <pgman@candle.pha.pa.us>,
	PostgreSQL General <pgsql-general@postgresql.org>
In-Reply-To: <2711.1147449236@sss.pgh.pa.us>
References: <C08A0257.49C30%scott_ribe@killerbytes.com>
	<C08A0257.49C30%scott_ribe@killerbytes.com>
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At 11:53 AM 5/12/2006 -0400, Tom Lane wrote:

>Scott Ribe <scott_ribe@killerbytes.com> writes:
> >> My damn powerbook drive recently failed with very little warning
>
> > It seems to me that S.M.A.R.T. reporting is a crock of shit. I've had ATA
> > drives report everything OK while clearly in the final throes of death, 
> just
> > minutes before total failure.
>
>FWIW, I replaced a powerbook's drive about two weeks ago myself, and its
>SMART reporting didn't show a darn thing wrong either.  Fortunately, the
>drive started acting noticeably weird (long pauses seemingly trying to
>recalibrate itself) while still working well enough that I was able to
>get everything copied off it.  I didn't wait for it to fail completely ;-)

Strange. With long pauses, usually you'd see stuff like "crc" errors in the 
logs, and you'd get some info from the SMART monitoring stuff.

I guess a lot of it depends on the drive model and manufacturer.

SMART reporting is better than nothing, and it's actually not too bad. It's 
just whether manufacturers implement it in useful ways or not.

I wouldn't trust the drive or manufacturer's judgement on when failure is 
imminent - the drive usually gathers statistics etc and these are typically 
readable with the SMART monitoring/reporting software, so you should check 
those stats and decide for yourself when failure is imminent.

For example: I'd suggest regarding any non-cable related CRC errors, or 
seek failures as "drive replacement time"- even if the drive or 
Manufacturer thinks you need to have tons in a row for "failure imminent".

I recommend "blacklisting" drives which don't notice anything before it is 
too late. e.g. even if it starts taking a long time to read a block, it 
reports no differences in the SMART stats.

Link.