[DRBD-user] dual primary mode with which FS

Christian Iversen chrivers at iversen-net.dk
Wed Mar 24 09:50:44 CET 2010

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


On 2010-03-24 08:05, Stefan Seifert wrote:
> On Tuesday 23 March 2010 22:57:39 Christian Iversen wrote:
>
>> Well, there's that. But the *primary* can't change anything either! Data
>> would change while the filesystem expects it not to. Even if you somehow
>> disable all caching (which you can't do without changing the kernel),
>> you would STILL get serious data corruption errors, because of the many
>> possible race conditions.
>>
>>> It's not wise, but it's not impossible, either.
>>
>> It is impossible, though. Unless NEITHER node ever change the data. And
>> in that case, you might as well just copy it out once and for all.
>
> If one really wants to read on the secondary there's an easy way: put DRBD on
> top of LVM and create a snapshot and mount that ro. Works just as one would
> expect including the absolutely obvious side effects of working with a
> snapshot like having to recreate it to get updated data. And even the sysadmin
> two generations from now will immediately understand this.

Are you sure that LVM can create the snapshot without updating the 
metadata on the device? Because that's not allowed.

-- 
Med venlig hilsen
Christian Iversen



More information about the drbd-user mailing list