Maximum volume size on DRBD

From time to time we get asked things like this:

I want to use a 10TiB volume with DRBD, is that supported”?

The easiest way to answer things like that is to say look for yourself on the public DRBD usage page – the biggest public device size is ~220TiB, so go figure 😉 (JUNE 2019 UPDATE: The largest device is now up to 600 TiB.)

The current maximum device size is 1PiB (1 PetiByte = 1024 TibiByte[1. Yes, I like “Tera”, “Peta” and “Exa” more, too.]), so there’s a bit of room left.

DRBD needs about 32MiB RAM per TiB storage; so for 1PiB storage you are at 32GiB just for the DRBD bitmap[1. at least with current code, we’ll have to change that for really big devices]. Having a bit more for the OS, userspace and buffer cache is left as an exercise for the reader.

If you’ve got questions, ask the DRBD experts at LINBIT – we wrote the code, after all!

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