Message-ID: <49405A94.8080601@tmr.com>
Date: Wed, 10 Dec 2008 19:11:00 -0500
From: Bill Davidsen <davidsen@tmr.com>
Organization: TMR Associates Inc, Schenectady NY
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To: Justin Piszcz <jpiszcz@lucidpixels.com>
CC: linux-kernel@vger.kernel.org, linux-raid@vger.kernel.org, xfs@oss.sgi.com,
       smartmontools-support@lists.sourceforge.net
Subject: Re: Have the velociraptors in a test system now, checkout the errors.
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Justin Piszcz wrote:
> Point of thread: Two problems, mentioned in detail below, NCQ in Linux 
> when used in a RAID configuration and two, something with how Linux 
> interacts with the drives causes lots of problems as when I run the WD 
> tools on the disks, they do not show any errors.
>
> If anyone has/would like me to run any debugging/patches/etc on this 
> system feel free to suggest/send me things to try out.  After I put 
> the VR's in a test system, I left NCQ enabled and I made a 10 disk 
> raid5 to see how fast I could get it to fail, I ran bonnie++ shown 
> below as a disk benchmark/stress test:
>
> For the next test I will repeat this one but with NCQ disabled, having 
> NCQ enabled makes it fail very easily.  Then I want to re-run the test 
> with RAID6.
>
> bonnie++ -d /r1/test -s 1000G -m p63 -n 16:100000:16:64
>
> $ df -h
> /dev/md3              2.5T  5.5M  2.5T   1% /r1
>
> And the results?  Two disk "failures" according to md/Linux within a 
> few hours as shown below:
>
> Note, the NCQ-related errors are what I talk about all of the time, if 
> you use
> NCQ and Linux in a RAID environment with WD drives, well-- good luck.
>
> Two-disks failed out of the RAID5 and I currentlty cannot even 'see' 
> one of the drives with smartctl, will reboot the host and check sde 
> again.
>
> After a reboot, it comes up and has no errors, really makes one wonder 
> where/what the bugs is/are, there are two I can see:
> 1. NCQ issue on at least WD drives in Linux in SW md/RAID
> 2. Velociraptor/other disks reporting all kinds of sector errors etc, 
> but when you use the WD 11.x disk tools program and run all of their 
> tests it says the disks have no problems whatsoever!  The smart 
> statistics do confirm this.  Currently, TLER is on for all disks, for 
> the duration of these tests.

Just a few comments on this, I have several RAID arrays built on Seagate 
using NCQ, and yet to have a problem. I have NCQ on with my WD drives, 
non-RAID, and haven't had an issue with them either. The WDs run a lot 
cooler than the SG, but they are probably getting less use, as well. If 
the WD are still on sale after the holiday I may grab a few more and run 
RAID, by then I will have some small sense of trusting them.

-- 
Bill Davidsen <davidsen@tmr.com>
  "Woe unto the statesman who makes war without a reason that will still
  be valid when the war is over..." Otto von Bismark 


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