[DRBD-user] Is `sync` option of ext3 mount SHOULD used in drbd HA clusters?

Pan'ko Alexandr A.Panko at infocom.dn.ua
Mon Sep 15 14:55:55 CEST 2008

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


Let's see article from 

Let's do commands:

[root at node1 /]# drbdadm primary repdata ; mount /dev/drbd0 /repdata
[root at node1 /]# dd if=/dev/urandom of=/repdata/test.file  bs=1000000c
count=1000; ip l set eth0 down;
[root at node1 /]# ls -l /repdata/test.file
-rw-r--r-- 1 user users 1000000000 Sep 15 15:07 /repdata/test.file

[root at node2 /]# drbdadm primary repdata ; mount /dev/drbd0 /repdata
[root at node2 /]# ls -l /repdata/test.file
-rw-r--r-- 1 user users 868456004 Sep 15 15:07 /repdata/test.file

As you will see there will be different sizes.
But they SHOULD be the same.

If we will add to mount command the option '-o sync', than there will
be no differences in sizes. But in case of 'bs=1c' in dd command the
file creation will be very and very slow because of turned off chaching.

Anybody knows this issue?
SHOULD I turn off caching om ALL underling devices and filesystems to
get HA cluster filesystem?

Regards, Alexandr A. Panko

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