On 2009-09-15 00:48, Christian Iversen wrote: > Hey DRBD-list > > I'm trying to build a reasonably performant DRBD-minicluster (2 machines > with heartbeat). I've got the basic setup working fine, with 2 largely > identical servers each running a Seagate 7200.ES 500GB disk. > > This is exported as a HA-NFS on top of the 500GB DRBD volume with > internal metadata. It's used in our production system, and we're > generally very happy with the result (failover, etc), except the > performance leaves a bit to be desired. > > I have a few questions: > > 1) It really seems internal metadata is a bad idea, since it eats 2 > extra seeks per write. Is this always true, or can DRBD sometimes buffer > these metadata-writes to minimize impact?
Can you please google 'drbd "internal metadata"' and hit "I'm Feeling Lucky"? > 2) Suppose write latency (related to question #1) is our biggest > concern. We are currently using protocol C. Will protocol A or B be > vastly different? I know there's no substitute for a proper > benchmarking, but we are a little wary of "just testing something" on > our production system. Does anybody have experience with this they would > like to share? You answered that question yourself: > P.S: I should note that we are not willing to sacrifice data integrity > for performance. If it seems that way from my comments about protocol > A/B/C, let me assure you that we simply want to learn about the various > bottlenecks in the system. C is the *only* protocol that guarantees data integrity. Thus, A and B are irrelevant to you. > > 3) Suppose the write latency really is the biggest problem we're facing > (we're still investigating the situation). As far as I can tell, a > battery-backed storage controller is the way to go, since this will > allow persistent stores to complete right away. However, this is for a > normal server, not DRBD. How does DRBD affect this situation? Will such > a controller even be useful at all? Answered in the same blog post your Google search will lead you to. Cheers, Florian
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