[DRBD-user] Disk Corruption = DRBD Failure?

Charles Kozler charles at fixflyer.com
Fri Oct 14 14:36:39 CEST 2011

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


Hi Florian,

Thanks again for all of your help.

While the diagram makes clear the entire flow of the process, I am 
looking for something like a flow chart to depict the order of 
operations. For instance, what is the flow of the data and order of 
operations when a write occurs to /dev/drbd0 on the primary and how is 
it applied on the other node- a write occurs to /dev/drbd0 on node1, it 
writes to the real block device on node1, then is put on the socket to 
node2, node2 receives data and applies algo check (if applied), data 
written to /dev/drbd0 on node2.

The fundamentals page also only gives a brief overview of how it works 
at a high level, I am looking to see what actually occurs under the hood 
so perhaps I should start looking at the kernel docs that you pointed 
out earlier?



Regards,
Chuck Kozler
/Lead Infrastructure & Systems Administrator/
---
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FIX Flyer

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On 10/14/2011 5:21 AM, Charles Kozler wrote:
> Haven't read it yet though I will later today.
>
> Having not ready any of the documentation of the underlying processes/workings, all of my understandings were purely based on assumptions from my basic use with DRBD- that said, thank you for all your insight and I will let you know later my understandings :)
>
>
> Sent from my Verizon Wireless BlackBerry
>
> -----Original Message-----
> From: Florian Haas<florian at hastexo.com>
> Sender: drbd-user-bounces at lists.linbit.com
> Date: Fri, 14 Oct 2011 09:08:17
> To:<drbd-user at lists.linbit.com>
> Subject: Re: [DRBD-user] Disk Corruption = DRBD Failure?
>
> On 2011-10-12 20:30, Charles Kozler wrote:
>> I will re-read the DRBD Funadmentals- the way I understood it was
>> basically if you were writing to node1 it wouldn't put the data through
>> a TCP socket and would actually just write directly to the block device
>> and that TCP was usually only used for the actual replicating and data
>> integrity conversation between the hosts.  My understanding now is that
>> for all hosts included in the resource definition it will put the data
>> into that socket - including the host you're writing from (eg: if I
>> wrote to /dev/drbd0 on host1 it will go through the socket to write the
>> data still to write it to the underlying block device-
> Er, no. It won't.
>
>> I had originally
>> thought it would skip the TCP socket write and write directly to the
>> block device).
> For the _local_ write, of course it doesn't go through the TCP socket.
> Why should it? That would be braindead. Also, given the documentation,
> what makes you think so? I ask because I wrote it, and if there's
> anything horribly unclear in there I'd be happy to fix it.
>
> Did you look at the illustration in the Fundamentals chapter?
>
> Florian
>
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