[DRBD-user] peer-max-bio-size 1M

Lars Ellenberg lars.ellenberg at linbit.com
Fri Apr 11 09:02:32 CEST 2014

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

On Thu, Apr 10, 2014 at 03:59:36PM +0200, Ben RUBSON wrote:
> Hello,
> According to drbdmeta manpage :
> If you will use the resource before it is connected to its peer for the
> first time DRBD may perform better if you use the --peer-max-bio-size
> option. For DRBD versions of the peer use up to these values: <8.3.7 -> 4k,
> 8.3.8 -> 32k, 8.3.9 -> 128k, 8.4.0 -> 1M.
> So as I use 8.4.4 on both nodes, here is my drbdmeta command :
> drbdmeta 0 v08 /dev/c0v0 internal create-md --peer-max-bio-size 1M
> --al-stripes 4 --al-stripe-size-kB 32
> Result :
> peer-max-bio-size out of range (0...128k)
> Did I miss something ?

That's apparently an oversight (Bug),
there is still a value of 128k hardcoded in drbdmeta.

> Will both nodes discuss about the value to use up to 1M, even if I don't
> use "--peer-max-bio-size 1M" in drbdmeta ?

If you have two nodes,
don't use that option to drbdmeta.

That option to drbdmeta should NEVER be used,
UNLESS you set up a single node DRBD and start to use it as single node,
before you even configure and connect the peer.

> I wait for your answer to create my resources :-)

For any normal use case, using that option to drbdmeta is simply wrong.
So don't.


: Lars Ellenberg
: LINBIT | Your Way to High Availability
: DRBD/HA support and consulting http://www.linbit.com

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