[DRBD-user] drbd + 10gig network

Igor Neves igor at 3gnt.net
Mon Nov 2 11:20:06 CET 2009

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

On 10/30/2009 07:52 PM, Mike Lovell wrote:
> Todd Denniston wrote:
>> Mike Lovell wrote, On 12/23/-28158 02:59 PM:
>>>> On 10/23/2009 10:40 PM, Mike Lovell wrote:
>>>>> exaggerated the problem. when the sync hangs, the drbd module is 
>>>>> almost completely unresponsive. i tried doing a pause-sync and 
>>>>> then resume-sync thinking that it would nudge the module into 
>>>>> working but the commands timeout on talking to the module. i can 
>>>>> still cat /proc/drbd but that is about it until i take down the 
>>>>> network interface and drbd detects the network change. if i then 
>>>>> bring back up the interface, drbd detects it can talk again but 
>>>>> then only syncs a couple of megabytes before stalling again. i 
>>>>> have tried every way i can think of to check the integrity of the 
>>>>> network link between the hosts and everything says they are fine 
>>>>> except for during a ping flood there will be a few out of a couple h
>>> yes, i am using software raid. i guess i didn't try changing that 
>>> during my hardware changes. i'll see if i can scrounge up some raid 
>>> controllers to test this with.
>>> mike
>> One other thing I would suggest looking at, which I don't think 
>> anyone else mentioned.
>> Network equipment in between the mirrors. (switches, cables, crossovers)
>> What is your MTU?
>> I experienced a problem _very_ similar with the set I maintained when 
>> a 10/100baseT hub/switch was placed between the units instead of the 
>> crossover cable I had been using.  The base problem was that the hub 
>> only supported MTUs smaller than 1500, and I was using 6000.  If you 
>> are using Gig equipment I would expect a considerably larger maximum 
>> MTU, but there _may_ be a limit somewhere there.
>> hope this helps.
> i am essentially using a crossover cable between the boxes and a mtu 
> of 9000. i did try with the standard 1500 and 9000 frame sizes and had 
> failures with both.
> mike

In my opinion, you should put everything on the default standard's. MTU 
should only be changed when you need "the extra mile" and AFTER you have 
your system stable.

Don't change default's before your have that stability. You don't get so 
much difference in speed changing MTU from 1500 to 9000.

This is my rule when i'm having troubles or when I'm playing with 
something new, and this is for all options, don't apply only for MTU.

I will be playing exacly with this setup one of this days, I will give 
my feedback later.

Have you consider using EL5 (or centos 5)?

Good luck,

Igor Neves<igor.neves at 3gnt.net>
3GNTW - Tecnologias de Informação, Lda

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