Re: [Nbd] Performance numbers?
Brought to you by:
yoe
|
From: Dirk v. S. <dir...@rz...> - 2008-09-21 00:15:18
|
Hi! > > Does anyone have any performance numbers on nbd vs things like nfs, > > san vendor offerings, etc? > > Linux magazine did an article about netbooting diskless clients a few > years ago, and that has some comparative numbers between NFS, NBD, and a > bunch of other variants of NBD. I'm offline right now and don't have the > URL with me, but there's a link on <http://nbd.sf.net/>. Other than > that, I'm not aware of any performance comparisons; but my gut feeling > is that NBD is probably faster, since the protocol is so extremely > simple and low overhead. I was the one who did some tests for that article :) But the setup was quite special: Running NFS-RO vs. NBD/SquashFS (RO because of SquashFS). The NBD/SquashFS produced ~1/2 - 2/3 of traffic compared to NFS (simple machine bootups) and was few seconds faster in startup. Later on another student wrote a DNBD2 (special RO blockdevice using UDP) which offers failover and load balancing and was faster on Gigabit links. For some reason we were not able to saturate a gigabit ethernet with NBD (never investigated too deeply into that one). For some tests you might want to have a glance at: http://www.ks.uni-freiburg.de/download/bachelorarbeit/SS07/06-07-dnbd2-dileo If you would like to tryout the DNBD2 I can find the link to a patched version for newer kernels. > > How about information on failover of an nbd 'server' from one machine > > to another? > > Why the quotes? > > I'm not entirely sure on what you mean with failover. If you mean having > an NBD client connected to one machine automatically reconnecting to > another when its server goes down, then there currently is no support > for that. A while back there was talk about having the kernel module > block access to the block device until the client exits; I don't know > what happened to that, but if it got merged, then it should be > reasonably straightforward to implement failover as part of nbd-client. We have it here for read-only (DNBD2 -> http://openslx.org/trac/de/openslx/browser/contrib/dnbd2) > Having said that, it is perfectly possible to create a failover cluster > with RAID-over-NBD and heartbeat. To do that, you'd run a software RAID1 > over a local block device on the one hand and an NBD device on the > other; the other machine would run nbd-server, and you'd switch places > when heartbeat tells us that the machine running the RAID1 is dead. The DNBD2 is able to monitor a number of different servers and choose the fastest one for service. Quite nice in larger setups. Good night! Dirk |