Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
On Fri, Nov 18, 2011 at 1:55 AM, Florian Haas <florian at hastexo.com> wrote: > Hi Trey, > > On 11/18/11 07:22, Trey Dockendorf wrote: > > In preparation to begin testing DRBD I've found my superiors have new > > requirements. The desired setup is 3 nodes in the cluster, replicating > > a LVM volume between all 3. The volume will contain QCOW2 images for > > KVM, and to have concurrent access I've been looking at using GFS2. > > OK, so if it's 3 nodes that a hypervisor is meant to run on, then that > rules out putting DRBD-based storage and the hypervisors on the same > boxes. (It certainly doesn't rule out the use of DRBD altogether; see > below). > > > The potential complication is all 3 servers are not identical. Two are > > identical, Dell 2950s. The other is a new Dell R510. The 2950s run 6 x > > SATA 7200RPM in RAID 6, and the R510 has it's system on RAID1 SAS and 6 > > x SAS 10000RPM in RAID 6. Is it correct that with DRBD, the combination > > of mismatched performance of the disk I/O would be a problem? How much > > more difficult is a 3 node cluster over 2 node? > > For multiple-node write access, it's impossible. What DRBD currently > supports is adding a third node in a stacked configuration, but that is > only useful for backup and DR purposes. You can't really think of the > third node as a fully-fledged member of the virtualization cluster. > > > Also, if I'm able get an iSCSI, what role would DRBD play in the model > > of 3 servers w/ shared storage? I assume to allow concurrent access to > > the same iSCSI space, that I would have to still use a cluster file > > system (live migration). Would DRBD then be used to replicate the > > system partitions or with KVM is it only useful to replicate the VM > > store when not using shared storage? > > You can put your iSCSI on DRBD-backed storage, and then use that iSCSI > target as centralized storage for your hypervisors. You may not even > need to set up cLVM. That's what this talk explains: > > http://www.hastexo.com/content/roll-your-own-cloud > > (Free-of-charge registration required, or just use your Google Profile > or WordPress account, or anything else that supports OpenID, to log in.) > > You can also take a look at this Tech Guide which I wrote while working > at Linbit, which is still hosted on their site: > > > http://www.linbit.com/en/education/tech-guides/highly-available-virtualization-with-kvm-iscsi-pacemaker/ > > > With or without a shared storage device (most likely without), how would > > failover work for the virtual servers? Is that where Pacemaker comes > > in? Basically a way to trigger the still-alive servers to bring up the > > VMs that were running on the failed server. > > Yes, watch the talk. :) > > Cheers, > Florian > > -- > Need help with High Availability? > http://www.hastexo.com/now > _______________________________________________ > drbd-user mailing list > drbd-user at lists.linbit.com > http://lists.linbit.com/mailman/listinfo/drbd-user > Thanks for the info! This will keep me busy with research and testing, and hopefully allow me create a proper infrastructure plan. Thanks again, - Trey -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.linbit.com/pipermail/drbd-user/attachments/20111121/c5d98e30/attachment.htm>