[DRBD-user] What to do about read errors on the primary?

Arnold Krille arnold at arnoldarts.de
Tue Sep 18 01:20:23 CEST 2012

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


On Mon, 17 Sep 2012 16:04:09 -0600 Alan Robertson <alanr at unix.sh> wrote:
> I have read errors on the primary side, which caused the secondary to
> go into an "inconsistent" state.  This means that the disk which
> desperately needs backing up, is no longer being backed up (!).
> In an ideal world,

In an ideal world, and also in reality by the way, you would trow out
this broken disk and resync from the slave or restore from backup.

Also please repeat after me: A mirror/raid1 is _not_ a backup.

> it seems to me what one would like for DRBD to do
> would be:
>     get the data from the secondary

Detach the disk on the primary: "drbdadm detach <resource>"

>     write it to the primary - which often "fixes" read errors
>     continue on syncing everything else to the secondary
> How do I get it to do these things?  Or tell me why I don't really
> want this behavior?

No, don't do any of this. Move all services to the secondary, change
the disk on the then former primary and let it sync onto the new disk.

Good luck,

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