[DRBD-user] Meta data 'internal' or disk partition?

Lars Ellenberg Lars.Ellenberg at linbit.com
Mon Jan 8 13:43:48 CET 2007


/ 2007-01-08 11:28:40 +0000
\ James Vanns:
> 8.0rc1 boasts the ability to store the meta data info on a dedicated
> partition. Before I attempt to migrate the internal meta data at the
> end (last 128M of the disk used for the drbd device?) to a dedicated
> partition can anyone comment as to whether or not this is worth it?

> What are the benefits?

transparency: you don't have to think about where or how to create your
file system, the block device looks the same whether or not you have
drbd in the stack.

"resizing" gets much easier.

more flexible: you could have storage on raid5, meta data on raid10.

drbd transactional meta data updates introduce additional latency into
your write path. if meta data and storage area share the same "spindle",
the additional seek times involved don't help to reduce the overhead...

> What are the drawbacks?

you need an additional block device. easy with lvm.

> Is the 'internal' meta data replicated with the rest of the disk
> blocks underlying the drbd device?

no, of course not.
this meta data is node specific.

-- 
: Lars Ellenberg                            Tel +43-1-8178292-0  :
: LINBIT Information Technologies GmbH      Fax +43-1-8178292-82 :
: Vivenotgasse 48, A-1120 Vienna/Europe    http://www.linbit.com :
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