[DRBD-user] Why use DRBD and not mdadm raid1 for host based mirroring?

Lars Ellenberg lars.ellenberg at linbit.com
Fri Jun 27 13:37:20 CEST 2014

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

On Thu, Jun 26, 2014 at 09:12:40AM -0400, Allen Chen wrote:
> >When replying, please edit your Subject line so it is more specific
> >than "Re: Contents of drbd-user digest..."

Learn To Quote ^^^

> >This is host based mirroring.
> >md raid1 is meant to do that.
> >Why not use it?
> >
> >Oh, so you want it async...
> >Did you know about mdadm "write-mostly" and "write-behind"?
> >
> >It's not that DRBD cannot do it.
> >It's just that I think it is the wrong tool for the job.
> >So please explain to me why you think otherwise.
> >
> >	Lars
> >
> Hi Lars,
> Here is my explanation to use DRBD instead of md raid1:
> for md raid1, if one member is physically removed from the machine,
> and after you reconnect the same disk to md raid1, MD will re-sync
> everything to it. It takes much more time.

meet mdadm --grow --bitmap internal

: Lars Ellenberg
: LINBIT | Your Way to High Availability
: DRBD/HA support and consulting http://www.linbit.com

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