Re: Cant make write cache stay on
From: James W. Long (JamesLong_at_wowway.com)
Date: 06/30/04
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Date: Wed, 30 Jun 2004 12:21:08 -0400
Dear Rick and Everyone:
"Rick" <me@privacy.net> wrote in message
news:OaGRkWnXEHA.2840@TK2MSFTNGP11.phx.gbl...
> What kind of drive is it, scsi? Check the setup options in
> the controller bios for a write cache option.
The BIOS setting enables/disables
actual hardware, Before the OS boot
ever gets a chance to look at it.
You can safely assume my BIOS
always allows write-cache hardware.
Thats not the problem.
Problem is this:
Because its a AD DC and sees no UPS
it won't allow a write cache, even though
it starts with one, it disables that right after winboot,
and puts an nice little message to the this effect
in my error log - "Because this machine is
a DC, Windows has disabled the write cache
on device /xxx" (boot drive).
I'll explain:
It was write cached before I upgraded.
The drive is a normal drive and has
hardware-write-cache capability.
Very few drives these days dont.
I upgraded from NT to Win2k Server,
I made it a Domain controller (DC).
When I did that, it installed Active Directory.
(AD). So its an AD DC. It wants to protect
a special database for AD on the boot device because
thats where I installed the AD database.
The AD database is crucial to the operation
of, you guessed it, an AD DC.
How does it protect the database?
Windows normally runs
with a write cache. BUT.. this is an AD DC Server!
microshaft says an AD DC Server has to take
"extra precaution" so it doesnt lose data.
Here it what it does. Windows looks for a
UPS (uninterruptable power supply) attached.
If it does not find one, it figures that if power
is lost, data stored in the normal write cache would
not be written to the hard disk when the thing
unexpectedly shuts off.
Thats one reason why a sudden power loss may corrupt your hard drive.
so....the AD Server domain controller takes a "pre-emptive"
step to make sure its data is ALWAYS up to date.
It disables write cacheing on the drive with the
AD database, forcing each write request to happen _now_
instead of later, using the cache as its normally done.
nifty huh.
NOT. Can you say SLOOOOOOOOOOW???
This is called microshaft "policy".
If the DC had detected a UPS then the write cache
(if enabled- you bet I enable it) would have stayed enabled.
I _could_ solve this by putting a UPS on the machine.
I don't have one and I don't plan on ever getting one.
I LIKE being without a UPS. Makes me shiver all over.
I never had one on this LAN in 5 years. Got it covered.
The point is it's NOT thier call. It's my call. It's my
server, my domain, my network, and my work.
winblows has a write-behind-cache built in.
I prefer to use it. I don't care what the policy is,
who made it, where it came from, or even why its
there because I disagree with prejudice.
Anyone ran into this or know how to get around it?
Thanks,
James
<snip>
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