[DRBD-user] Further investigation into verify problems

Ben Clewett ben at roadrunner.uk.com
Mon Mar 10 09:18:38 CET 2008

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.


Glad to supply as much information as you ask for.

First a discovery.  I was clearing the array by issuing on the primary:

# drbdadm disconnect all
# debdadm connect all

Which I found didn't work.  However if I do this on *both* primary and 
secondary, so that I disconnect both and then connect both, I do clear 
my bad blocks.

Other answers in line:

Florian Haas wrote:
> Ben,
> On Thursday 06 March 2008 18:17:42 Ben Clewett wrote:
>> Dear DRBD,
>> I am continuing to try and work out the verify on 8.2.5 from the manual:
>> http://www.drbd.org/users-guide/s-use-online-verify.html
>> The verify works and finds bad blocks.  However I can't seem to clear
>> them using the suggested method of disconnect and connect.  Further
>> verify commands seem to add bad blocks (on my set-up), which I could
>> only clear with a full invalidation.
>> I also did a check on all three suggested hashing algorithms, and found
>> they all showed the same load and time to complete.  Which was also
>> exactly the same load and time as a full invalidate.
>> So I am not sure what the advantage of the verify is.  
> The obvious advantage of online verify vs. "bulldozer-style" full resync is 
> this: While you are doing a full resync, since your Secondary is 
> inconsistent, you are not redundant. In other words if your Primary crashes 
> during the resync, you're in trouble... or at least forced to bust out your 
> tapes. While you are doing an online verify run, you are fully redundant the 
> whole time. 

I understand.

>> With the current
>> version on 8.2.5, it seems to promote the creation of bad blocks, does
>> not allow them to clear, and have the same time and loading as a full
>> resync.
>> I'm hoping you can tell me that I am doing something completely wrong.
> Nothing that occurs to me at first glance. But I have a few questions for you:
> - Can you confirm the behavior you described with protocol C, too? Or is this 
> only reproducible with protocol B? 

I will check over the course of today and let you know.

> - What is your particular reason for specifying the device size explicitly and 
> does the issue also appear when you don't?

The physical partition size is slightly different on both sides.  To 
avoid any problem I manually set the size at a few meg below the 
smallest size.

I can't change this on the hardware I have avaiable for testing very 
easily.  Unless DRBD is completelly safe when it finds different sized 

> - What specific make and model of SmartArray controller are you using, and 
> what is the firmware version and cciss driver version?

Both sides enjoy the same smart array which is up to latest firmware 

Smart Array P400 Firmweare 4.12 with RAID 5 over seven 136 GB SATA drives.

No problem, only trying to be helpful...


> Cheers,
> Florian

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