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Re: Write Verify and XFS

To: linux-xfs@xxxxxxxxxxx
Subject: Re: Write Verify and XFS
From: Derek Glidden <dglidden@xxxxxxxxxxxxxxx>
Date: 13 Feb 2003 11:49:19 -0500
In-reply-to: <3E4BC6D5.4090807@xxxxxxxxx>
References: <3E4BC1ED.3060201@xxxxxxxxxxxx> <3E4BC6D5.4090807@xxxxxxxxx>
Sender: linux-xfs-bounce@xxxxxxxxxxx
On Thu, 2003-02-13 at 11:24, Michael Sinz wrote:

> > Last question, if this -really- is normal, and it is something that has 
> > to be dealt with, what is the proper solution?  I know that leaving 
> > Write Verify turned on is not the solution.  It cuts drive performance 
> > in half. One proposed solution (for us at least) is to turn Write Verify 
> > on for "critical" data and off for "non-critical" data. This seems like 
> > a hack.  <RANT> If I write the data to the drive, and the drive says 
> > "OK" shouldn't the data be there? </RANT
> 
> I agree with your rant - and I also know that the trick the drive
> makers use works for Windows systems because the "format" operation
> (well older Windows) would write to every sector of the drive.

Agreed here also.
 
> What I have done is to take new drives and put them on-line (powered)
> and set the write verify on and then use a simple tool that wrote
> random data over the whole disk (or just /dev/zero using something

We typically run new systems through the "Cerberus" test, originally
made by VA.  One of the test processes does something similar to what
you're describing above, only doing multiple parallel non-destructive
reads against the whole block device, which also seriously stresses the
drive.  We've had great luck with Cerberus catching out marginal
equipment before we deploy new systems.

http://sourceforge.net/projects/va-ctcs/

We actually do use IDE drives for all our systems, but important systems
get pounded for some time with Cerberus, and at the very least get
mirrored drives if not RAID5.  I still agree that SCSI is "better" but
as long as we've gone through full QA, we've had great luck with IDE,
and IDE is just so much cheaper and considering the state of the
industry today....

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