[DRBD-user] read-only access on Secondary for MySQL (InnoDB) Raw Partition?

Lars Marowsky-Bree lmb at suse.de
Wed Jun 23 11:29:52 CEST 2004


On 2004-06-23T01:39:47,
   Josh McAllister <josh at bluehornet.com> said:

> I'm really not trying to be a pain in butt... just encouraging some
> "out-of-the-box" thinking... That being said, I've read the FAQ, the
> pertinent part:
> 
> "DRBD would not care, but most likely your filesystem will be confused
> because it will not be aware about changes in the underlying device.
> This in general means that it cannot work, not with ext2, ext3,
> reiserFS, JFS or XFS. If you need not just a mirrored, but a shared
> filesystem, use GFS or OpenGFS for example. But these are much slower."
> 
> In this case there is no "filesystem", we are accessing the partition
> directly, so if DRBD truly doesn't care...???

I doubt that MySQL likes to have it's files underneath it changed
either. You can of course go ahead and try it; a read-only access on the
secondary is possible. It'll likely crash MySQL.

A read/write access is more difficult to implement correctly
(synchronization between the nodes etc) and is not supported by drbd
(yet).

> "This is the reason why DRBD does not allow mounting the secondary."
> Is this arbitrary limitation really enforced?

It's not quite arbitrary, it tries to prevent you from shooting down
your data with a flak ;-)


Sincerely,
    Lars Marowsky-Brée <lmb at suse.de>

-- 
High Availability & Clustering	    \ ever tried. ever failed. no matter.
SUSE Labs, Research and Development | try again. fail again. fail better.
SUSE LINUX AG - A Novell company    \ 	-- Samuel Beckett




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