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Re: Turning off write protect of IDE drives hidden behind a 3ware contr

To: Greg Freemyer <freemyer@xxxxxxxxxxxxxxxxx>
Subject: Re: Turning off write protect of IDE drives hidden behind a 3ware controller? [WAS: recovery failed after power off]
From: Simon Matter <simon.matter@xxxxxxxxxxxxxxxx>
Date: Tue, 06 Aug 2002 13:58:00 +0200
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Greg Freemyer schrieb:
> 
>  >>  Greg Freemyer schrieb:
>  >>  >
>  >>  >  >>  On Fri, Aug 02, 2002 at 02:19:28PM +0200, Christian Thalinger
>  >>  wrote:
>  >>  >  >>  > Yep, IDE drive with write cache. Sorry, i could guess it myself.
>  >>  >  >>  > Without write cache recovery seems to be ok. Now i have to find
>  >>  out
>  >>  >  >>  > how to disable write cache of IDE drives on a 3ware controller
>  >>  ;-)
>  >>  >
>  >>  >  >>  This can be done both via the 3ware BIOS which you can enter at
>  >>  bootup,
>  >>  >  >>  or via the 3dmd web-based management system.
>  >>  >
>  >>  >  >>  --> Jijo
>  >>  >
>  >>  > I know that turns off the write cache on the 3ware controller itself.
>  >>  >
>  >>  > Does it also turn off the write cache on the underlying IDE drives?
> 
>  >>  There are tools around, usually from the drive vendor, with which you
>  >>  can change cache configuration. Unfortunately there are IDE drives
>  >>  around which don't disable write cache even if they are configured to do
>  >>  so.
> 
>  >>  Simon
> 
> Simon,
> 
> I believe the 3ware controller effectively hides the IDE nature of the drives 
> from the OS/bios and I doubt if the drive vendor's tools are smart enough to 
> work in a 3ware environment.

You're right.

> 
> Are you suggesting that in a 3ware environment, one should move the IDE 
> drives to a computer with standard IDE controllers;  turn off the write 
> cache, then move them back behind the 3ware controller?

Exactly.

> 
> I can see that working if the drives store that piece of their config in 
> Non-volatile RAM, but I don't have that level of knowledge.

There are several ways a harddisk can do this. The cheapest way would be
that the drive writes those configuration data on a reserved sector on
the disk. It doesn't matter how the drive does it, the only question is
whether the drive actually _does_ what it is configured to do.

Simon

> 
> If that is what needs to be done, I can certainly do it, but it does seem to 
> be a pain.
> 
> Greg Freemyer
> Internet Engineer
> Deployment and Integration Specialist
> Compaq ASE - Tru64 v4, v5
> Compaq Master ASE - SAN Architect
> The Norcross Group
> www.NorcrossGroup.com



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