[DRBD-user] Further investigation into verify problems

Florian Haas florian.haas at linbit.com
Mon Mar 10 09:09:16 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.


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. 

> 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? 

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

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


: Florian G. Haas
: LINBIT Information Technologies GmbH
: Vivenotgasse 48, A-1120 Vienna, Austria

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