[DRBD-user] DRBD serious locking due to TOE - UPDATE

Ben Clewett ben at roadrunner.uk.com
Tue Jan 8 16:02:53 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.

(Second send, used wrong email address :)

Hi Lars,

Lars Ellenberg wrote:
> grrr. stripp of one of the nots, please,
> either "not likely" or "likely not".
> anyways, it is NOT a problem in drbd.
> but you knew what I meant, right?

Many thanks, lots of good information to work with.

I knew what you meant.  I don't believe it is a problem with DRBD.  But
it manifests through DRBD.


There is a know problem with my NIC, even at
the latest driver:


However the suggested fix here doesn't make a difference:

# ethtool -K eth2 tso off

I have a known problem which does not respond to the known fix!

But I still suspect the NIC's...  Tonight I am going to move them all
around to see if the problem follows the card.


I also know that if I reboot the servers, I'll get a few days of grace
before the locking returns.  I don't think that is DRBD related?

I also note that slowing data input by introducing small 1
second gaps every half minute or so, actually increases the rate at
which data is accepted.  What could cause that affect?


The analysis of /proc/drbd shows data to be moving.  But I can see a

With my symmetrical system, on both servers:
# watch -n 0.1 -d cat /proc/drbd

The DRBD resource which is not 'locked' (drbd0) is moving data 
lo:1 is the normal condition, ns and dw are increasing linearly.

However the DRBD disk which is locked (drbd1) is only sporadically moved 
It can spend up to ~2 seconds stuck on:
	Primary:	bm:0 lo:n pe:0 ua:0 ap:n
	Secondary:	bm:0 lo:0 pe:0 ua:0 ap:0
Where n is some number between 1 and ~ 50.

It looks like the traffic flow from one server is blocking the traffic
flow from the another, like it has a higher priority?

This might also explain by introducing 1 second gaps helps get data 
moving, it stops one server letting the other work.

But it might also be coincidence...

I have checked my TCP shaping to ensure there is none.  Also set the 
fifo buffer in TCP 'bfifo' qdisc from 10K to 10M.  Makes no difference.

Besides which, I am only uses about 5% of bandwidth, so traffic shaping 
is irrelevant.


You also asked about mounting:

# cat /proc/mounts | grep drbd

/dev/drbd1 /dbms-07-02 reiserfs rw 0 0

Do you know of any options which might help?

Thanks again for your help,


Lars Ellenberg wrote:
> On Tue, Jan 08, 2008 at 12:21:21PM +0100, Lars Ellenberg wrote:
>> On Tue, Jan 08, 2008 at 09:06:44AM +0000, Ben Clewett wrote:
>>> Dear Lars,
>>> I found a server at lock when I got to my desk this morning.  Not wanting to
>>> waist any time, these are the numbers you ask for.
>>> Lock on 'hp-tm-02', twin with 'hp-tm-04' which is partially locked.
>>> I use the term 'lock' to explain a server with high load and very much
>>> reduced throughput.
>> as long as there is still throughput,
>> it is not likely not a problem in drbd.
> grrr. stripp of one of the nots, please,
> either "not likely" or "likely not".
> anyways, it is NOT a problem in drbd.
> but you knew what I meant, right?

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