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Date:      Fri, 07 Apr 2000 15:31:07 +0100
From:      "Koster, K.J." <K.J.Koster@kpn.com>
To:        "'Bob.Gorichanaz@midata.com'" <Bob.Gorichanaz@midata.com>
Cc:        'FreeBSD Hackers mailing list' <freebsd-hackers@freebsd.org>
Subject:   RE: bad memory patch?
Message-ID:  <59063B5B4D98D311BC0D0001FA7E452201313A80@l04.research.kpn.com>

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> 
> Not trying to push this idea one way or the other, I'm just 
> curious as to WHY so many people think this is a "bad idea"
> 
I can think of four things real quick:

1) Disks are much slowere, and controllers actually have time to do proper
error detection. Memory is built for raw, blind speed. The analogy that
memory is a disk does not hold for long.

2) Testing memory is a nightmare. It's virtually impossible to test your RAM
and guarantee it is right.  If the memory test tells you your RAM is broken,
you have to replace it. If it tells you your RAM is fine, it may or may not
be fine. Much like a pregnancy test. :-) Thus, expecting the OS to find and
mark bad memory for you will give you a false sense of security.

2) Working around bad blocks in disks is a stop-gap measure, but a
neccessary evil. You need it to be able to limp along until it is 9:00 am
Monday morning and the shops open for you to buy a new disk. (Head crashes
are chiefly caused by the late saturday *click* of the lock on the doors of
CompUSA). With RAM, that situation does not occur, because there is no user
data in RAM. You can rip a memory module out of any old server that's lying
around and get the machine back on line in minutes. You can halve the number
of memory modules in a server, and it will run as before (if a little
slower).

3) Claiming that FreeBSD will run fine on bad hardware is asking for
trouble. Use your imagination. Think "screwdriver".

    Kees Jan

PS. If you have only a single memory module in your box, well, sorry. Now
you know why I buy two. :-)

==============================================
 You are only young once,
      but you can stay immature all your life


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