[DRBD-user] block size

Philipp Reisner philipp.reisner at linbit.com
Thu Mar 25 15:02:42 CET 2004


Am Mittwoch, 24. März 2004 03:14 schrieb Jim Richard:
> using 0.6.12 source from 10 March 2004
>
> I notice on the terminal's of my 2 nodes that when I do a datadisk stop
> on primary and then datadisk start on the secondary, the roles
> (primary/secondary) switch (that's what I expect) and then on the
> terminal of the old primary (the one that just became secondary because
>   the other node did a datadisk start) I see:
>
> drbd0: blksize=1024 B
> drbd0: blksize=4096 B
>

This happens when a ext2/3 FS is mounted (maybe also on unmount).
The FS switches the IO subsystem in 1K mode to read the superblock, and
switches it back into 4K mode for further FS operation...

> what's that about, do I need to be concerned about mismatched blocksizes
> on the lower level devices of my 2 physical devices ?
>
> Also, do I understand that sync direction is always Primary to Secondary
> or at least is that the default operation ? i.e you control sync
> direction by setting primary/secondary ....

Right. This is true for drbd-0.6.x

-Philipp
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