Helps if I send this to the list... ---------- Forwarded message ---------- From: Nathan Cerny <[email protected]> Date: Mon, Apr 4, 2011 at 4:54 PM Subject: Re: [DRBD-user] DRBD primary/primary vs. VMFS3 ? To: pberton <[email protected]>
You have to run Protocol C to do primary/primary. Protocol C ensures both nodes know of each block write before it's reported as complete. So in your instance, one VM would get the block, and another would get a different block. There is no chance of them both reserving the same block. At least that's how I understand Protocol C. I'm sure someone else will correct me if I'm mistaken! On Mon, Apr 4, 2011 at 11:33 AM, pberton <[email protected]> wrote: > > Hi folks! > I've read a few posts talking about DRBD vs. VMFS3, but none seem to answer > my question. May be someone can help. Here's the picture : > I'm thinking of a primary/primary config, with ESXs on both sides. If > hosted > VMs do snapshots or make use of thin disks on both sides, corresponding > files will grow step by step or should I say, block by block, each new > block > allocation being securized using SCSI reservations from the host running > that VM. > Now, guess 2 VMs on different sides of the replication chain make a new > block request at the same time. What would happen ? I suppose SCSI > reservations are not replicated by DRBD, therefore, each host will make its > own reservation and potentially allow the same block to both VMs leading to > corruption ? > Has anyone already played with this kind of architecture ? Is > primary/primary definitely a no-no for such architectures or is there some > magic feature that can help me out build something safe ? > Thanks by advance! > Best regards, > Pascal. > -- > View this message in context: > http://old.nabble.com/DRBD-primary-primary-vs.-VMFS3---tp31315179p31315179.html > Sent from the DRBD - User mailing list archive at Nabble.com. > > _______________________________________________ > drbd-user mailing list > [email protected] > http://lists.linbit.com/mailman/listinfo/drbd-user > -- Nathan Cerny ------------------------------------------------------------------------------- "I have always wished that my computer would be as easy to use as my telephone. My wish has come true. I no longer know how to use my telephone." --Bjarne Stroustrup, Danish computer scientist ------------------------------------------------------------------------------- -- Nathan Cerny ------------------------------------------------------------------------------- "I have always wished that my computer would be as easy to use as my telephone. My wish has come true. I no longer know how to use my telephone." --Bjarne Stroustrup, Danish computer scientist -------------------------------------------------------------------------------
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