Messages in this thread | | | From | Philipp Reisner <> | Subject | Re: [PATCH 00/16] DRBD: a block device for HA clusters | Date | Tue, 5 May 2009 17:56:28 +0200 |
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On Tuesday 05 May 2009 16:09:45 James Bottomley wrote: > On Tue, 2009-05-05 at 10:21 +0200, Philipp Reisner wrote: > > > > When you do asynchronous replication, how do you ensure that implicit > > > > write-after-write dependencies in the stream of writes you get from > > > > the file system above, are not violated on the secondary ? > > > [...] > > > The way nbd does it (in the updated tools is to use DIRECT_IO and > > > fsync). > > [...] > I think you'll find the dio/fsync method above actually does solve all > of these issues (mainly because it enforces the semantics from top to > bottom in the stack). I agree one could use more elaborate semantics > like you do for drbd, but since the simple ones worked efficiently for > md/nbd, there didn't seem to be much point. >
Do I get it right, that you enforce the exact same write order on the secondary node as the stream of writes was comming in on the primary?
Using either DIRECT_IO or fsync() calls ?
Is DIRECT_IO/fsync() enabled by default ?
-Phil -- : Dipl-Ing Philipp Reisner : LINBIT | Your Way to High Availability : Tel: +43-1-8178292-50, Fax: +43-1-8178292-82 : http://www.linbit.com
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