[DRBD-user] Moving TeraBytes to drbd device

José Andrés Matamoros Guevara amatamoros at ie.com.sv
Thu Oct 5 05:29:00 CEST 2017

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

Thanks for your answer.

Yes, I need to copy a SAN to a new drbd system. And yes, I'll check with
LinBit for support if I don't find a safe solution for myself.

Just a question: I have been looking through the LinBit documents and
haven't found exactly what I was looking for. If you can point me about what
document/documents or topics I have to read about, will be great.

Thanks for the info.


-----Original Message-----
From: Digimer [mailto:lists at alteeve.ca] 
Sent: Tuesday, 3 October, 2017 6:10 PM
To: José Andrés Matamoros Guevara <amatamoros at ie.com.sv>;
drbd-user at lists.linbit.com
Subject: Re: [DRBD-user] Moving TeraBytes to drbd device

On 2017-10-03 06:57 PM, José Andrés Matamoros Guevara wrote:
> I have been consulted about moving multiple Terabytes to a new system 
> using drbd to ensure high availability. I have been thinking on 
> multiple scenarios to move the data as fast as I can and to have a 
> minimal maintenance window to change the systems.
> Is there any how-to or recommendation about it? I know it is not 
> exactly a drbd consult but I supposed you have been using it for a 
> while and have more idea about a best practice. I have thought to have 
> a backup program to copy the data and then update it during the 
> maintenance window, but been lots of TB, the reading/writing data time 
> is going to be the factor to consider.
> Thanks in advance and best regards, Andres.

The best answer is to engage LINBIT for commercial support if you've been
tasked with a sensitive project and a minimal window to do it in.

That said, I'll share what comes to mind;

If you mean "move" as in "copy the data to a new system that already has
DRBD configured and tested", then it is merely a question of hardware.
Make sure you have a sufficiently fast new system to accept the incoming
volume of data within the prescribed time frame. DRBD itself has minimal
overhead, so it is really a question of the speed of the disks and the
replication link.

If you mean to convert an existing filesystem on existing hardware to be
backed by DRBD, then you need to either grow the backing storage by ~32MiB
per TiB of existing data, or setup a matching sized storage device and
configure external metadata. With that extra space, you can setup DRBD and
it will see the existing FS and data fine. You'll need a full resync to the
new peer, of course. Also, test/practice outside prod thoroughly to be
certain you have the steps down pat.

There are docs on how to do this openly available on LINBIT's website.
If you get stuck on certain steps, post specific questions and we'll help.

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in the weight and convolutions of Einstein’s brain than in the near
certainty that people of equal talent have lived and died in cotton fields
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