[DRBD-user] Migrating NFS to a DRBD block device

Bernd Schubert bernd-schubert at web.de
Fri Oct 15 16:11:32 CEST 2004

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


Hello,

> NFS "handles" are in most implementations basically just
>  <block device number>:<inode number>, which is supposed to be unique,
> and  easily available.
>
> but this means that, if you change something on your nfs server,
> and now the data is on some other block device (drbd), the block device
> number changes, and thus all handles are invalid...
>
> if you change back, suddenly the handles are valid again.
>
> so there is no chance (without patching the nfs server to support a
> configurable mapping of exported handle numbers to block dev numbers)
> to migrate the data on the nfs server to some other block device without
> rebooting / forcefully remounting the clients.

I have currently not much time to give a detailed explanation how to solve 
this, Omar, could you try to search via google for my name and 'fsid'? I have 
answered this kind of question already at least two times in English. 
If you shouldn't find it, I will try to answer more in detail in about 6-7 
hours. 
The basic idea is to fake the fsid via the fsid mount option. 
You have to do this before you switch to drbd, so you set the fsid export 
option, reexport, remount from your clients on the fly and finally can switch 
the server to drbd.


Cheers,
 Bernd




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