Messages in this thread | | | Subject | Re: [PATCH 00/16] DRBD: a block device for HA clusters | From | James Bottomley <> | Date | Sun, 03 May 2009 09:21:14 -0500 |
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On Sat, 2009-05-02 at 22:40 -0700, david@lang.hm wrote: > On Sun, 3 May 2009, Willy Tarreau wrote: > > > On Sat, May 02, 2009 at 09:33:35AM +0200, Bart Van Assche wrote: > >> On Fri, May 1, 2009 at 10:59 AM, Andrew Morton > >> <akpm@linux-foundation.org> wrote: > >>> On Thu, 30 Apr 2009 13:26:36 +0200 Philipp Reisner <philipp.reisner@linbit.com> wrote: > >>> > >>>> This is a repost of DRBD > >>> > >>> Is it being used anywhere for anything? If so, where and what? > >> > >> One popular application is to run iSCSI and HA software on top of DRBD > >> in order to build a highly available iSCSI storage target. > > > > Confirmed, I have several customers who're doing exactly that. > > I will also say that there are a lot of us out here who would have a use > for DRDB in our HA setups, but have held off implementing it specificly > because it's not yet in the upstream kernel.
Actually, that's not a particularly strong reason because we already have an in-kernel replicator that has much of the functionality of drbd that you could use. The main reason for wanting drbd in kernel is that it has a *current* user base.
Both the in kernel md/nbd and drbd do sync and async replication with primary side bitmaps. The main differences are:
* md/nbd can do 1 to N replication, * drbd can do active/active replication (useful for cluster filesystems) * The chunk size of the md/nbd is tunable * With the updated nbd-tools, current md/nbd can do point in time rollback on transaction logged secondaries (a BCS requirement) * drbd manages the mirror state explicitly, md/nbd needs a user space helper
And probably a few others I forget.
James
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