[DRBD-user] DRBD is syncing extremely slow with slow media

Martin Peylo martinmeis at googlemail.com
Fri Apr 21 13:42:05 CEST 2006

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

Dear interested reader,

I'm trying to use DRBD on *CompactFlash* media. This kind of media is
extremely slow on write (~0,17 MB/s) and slow (~3.4 MB/s) on read - compared
with harddisks. They are formatted with reiserfs - that could explain the
extremely slow writing speed I got by using cp from ramdisk and calculating
the rate. But anyhow CF is very slow compared with harddisks.

I am using drbd 0.7.17 where I adjusted the size of the metadata to 2 MB
according to my earlier post

When I start syncing my 128MB flash drives it needs *hours* to finish and
not minutes as I expected.

I tried protocols A, B and C and I see no difference.

I tried to increase the buffers by doing e.g.:
drbdsetup /dev/drbd/0 net B -c 20 -e 16384 -b 16384
but I saw no difference. On all other settings I am using the standard

The connection between the machines is only 10Mbit right now for testing
purposes but I think that should be enough since the amount of data to be
transfered is really small.
The ping is below 0.4ms.

Has somebody any suggestions with what settings I could play around to
increase the speed?

I know that DRBD wasn't designed for slow media but I would also try to
improve the code - and for sure give my results back to the community - if
somebody would point me to a bottleneck in the current algorithm!

Warm regards, thank you and a nice weekend!
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