[DRBD-user] Questions regarding the initial syncing of a drbd partition

Roland Kammerer roland.kammerer at linbit.com
Fri Sep 11 16:00:47 CEST 2015

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

On Fri, Sep 11, 2015 at 03:09:21PM +0200, Lars Ellenberg wrote:
> On Thu, Sep 10, 2015 at 02:21:02PM +0200, Joerg May wrote:
> >   Would e.g. checksum-based syncing help to identify faster the free
> > blocks and skip them for syncing ?
> No.

- the rest (see later) of the source partition contains all zeros (or
  some other defined value) AND
- the partition on you new disk contains the same value AND
- your network is the bottleneck and not your CPU (e.g., overhead for
  calculating checksums).
then it might help.

Lots of ifs... For example you can not assume that your new disk
contains all zeros, there might be test-patterns from the factory and
what not. Or you usually can not assume that your old partition contains
all data at the beginning and the rest is "empty", there might be holes
not used by the file system that contain old garbage. How do you then
fill only the holes with the defined value?

So, as Lars said, in the usual case no, under certain conditions, yes.
-> truck based sync.

Regards, rck

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