RE: raid6 - data integrity issue - data mis-compare on rebuilding RAID 6 - with 100 Mb resync speed.

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>On Wed, Apr 23, 2014 at 03:03:21PM +0530, Manibalan P wrote:
>> >On Wed, Apr 23, 2014 at 02:55:15PM +0530, Manibalan P wrote:
>> >> >On Fri, Apr 11, 2014 at 05:41:12PM +0530, Manibalan P wrote:
>> >> >> Hi Neil,
>> >> >> 
>> >> >> Also, I found the data corruption issue on RHEL 6.5.
>> >> >> 
>> >> 
>> >> >Did you file a bug about the corruption to redhat bugzilla?
>> >> 
>>>> Yes, today I raised a support ticket with Redhat regarding this issue.
>>>> 
>> 
>> >Ok, good. Can you paste the bz# ?
>> 
>> https://access.redhat.com/support/cases/01080080/
>> 

>Hmm, I can't access that, do you have an url for bugzilla.redhat.com (which is the public bug tracker) ? 

https://bugzilla.redhat.com/show_bug.cgi?id=1090423

please look at the above link, I created one now.

Manibalan.
>-- Pasi

> manibalan
>  
> >
> >-- Pasi
> 
> > Manibalan
> > 
> > >-- Pasi
> > 
> > > For your kind attention, I up-ported the md code [raid5.c + 
> > > raid5.h] from FC11 kernel to CentOS 6.4, and there is no 
> > > mis-compare with the up-ported code.
> > > 
> > > Thanks,
> > > Manibalan.
> > > 
> > > -----Original Message-----
> > > From: Manibalan P
> > > Sent: Monday, March 24, 2014 6:46 PM
> > > To: 'linux-raid@xxxxxxxxxxxxxxx'
> > > Cc: neilb@xxxxxxx
> > > Subject: RE: raid6 - data integrity issue - data mis-compare on 
> > > rebuilding RAID 6 - with 100 Mb resync speed.
> > > 
> > > Hi,
> > > 
> > > I have performed the following tests to narrow down the integrity issue.
> > > 
> > > 1. RAID 6, single drive failure - NO ISSUE
> > > 	a. Running IO
> > > 	b. mdadm set faulty and remove a drive
> > > 	c. mdadm add the drive back
> > >  There is no mis-compare happen in this path.
> > > 
> > > 2. RAID 6, two drive failure - write during Degrade and verify 
> > > after rebuild
> > > 	a. remove two drives, to make the RAID array degraded.
> > > 	b. now run write IO write cycle, wait till the write cycle completes
> > > 	c. insert the drives back one by one, and wait till the re-build 
> > > completes and a RAID array become optimal.
> > > 	d. now perform the verification cycle.
> > > There is no mis-compare happened in this path also.
> > > 
> > > During All my test, the sync_Speed_max and min is set to 100Mb
> > > 
> > > So, as you referred in your previous mail, the corruption might be 
> > > happening only during resync and IO happens in parallel.
> > > 
> > > Also, I tested with upstream 2.6.32 kernel from git:
> > > "http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/ - 
> > > tags/v2.6.32"
> > > 	And I am facing mis-compare issue in this kernel as well.  on 
> > > RAID 6, two drive failure with high sync_speed.
> > > 
> > > Thanks,
> > > Manibalan.
> > > 
> > > -----Original Message-----
> > > From: NeilBrown [mailto:neilb@xxxxxxx]
> > > Sent: Thursday, March 13, 2014 11:49 AM
> > > To: Manibalan P
> > > Cc: linux-raid@xxxxxxxxxxxxxxx
> > > Subject: Re: raid6 - data integrity issue - data mis-compare on 
> > > rebuilding RAID 6 - with 100 Mb resync speed.
> > > 
> > > On Wed, 12 Mar 2014 13:09:28 +0530 "Manibalan P"
> > > <pmanibalan@xxxxxxxxxxxxxx>
> > > wrote:
> > > 
> > > > >
> > > > >Was the array fully synced before you started the test?
> > > > 
> > > > Yes , IO is started, only after the re-sync is completed.
> > > >  And to add more info,
> > > >              I am facing this mis-compare only with high resync 
> > > > speed (30M to 100M), I ran the same test with resync speed min 
> > > > -10M and max
> > > > - 30M, without any issue. So the  issue has relationship with 
> > > > sync_speed_max / min.
> > > 
> > > So presumably it is an interaction between recovery and IO.  Maybe 
> > > if we write to a stripe that is being recoverred, or recover a 
> > > stripe that is being written to, then something gets confused.
> > > 
> > > I'll have a look to see what I can find.
> > > 
> > > Thanks,
> > > NeilBrown
> > > --
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