I'm looking at converting all of our nginx caching servers over to varnish, but I'm seeing some oddities with the 'file' storage backend that I'm hoping someone could shed some light on.
Hardware specs for both machines: Dell PowerEdge R610 Dual Xeon E5620 @ 2.40GHz 64GiB memory 4x 240GB SSDs in a RAID5 attached to a PERC H700 RAID controller The following image compares CPU, memory, and IOPS for both a machine running varnish (left), and one running nginx (right): http://i1217.photobucket.com/albums/dd391/bstillwell_pb/Graphs/varnish-vs-nginx.png At the most recent sample, each machine was handling ~350 requests/sec. As you can see the varnish machine has a lot more CPU time dedicated to I/O wait, which matches up with ~5x higher IOPS numbers. However, the biggest difference is that varnish is using ~25x more read IOPS than nginx. As for the jumps in the IOPS graph, I believe they can be explained by: Wednesday @ 10:00a: Started taking traffic Wednesday @ 11:00a: Memory cache filled, started using SSDs Wednesday @ 4:00p: TTL of 6 hours was hit, objects start expiring Wednesday @ 7:15p: SSD cache filled I pre-allocated the storage with fallocate (fallocate -l 450g /cache/varnish_storage.bin) to make sure that wasn't helping contribute to the issue. Any ideas on what could be tuned to reduce the number of read IOPS to be more inline with nginx? Thanks, Bryan _______________________________________________ varnish-misc mailing list [email protected] https://www.varnish-cache.org/lists/mailman/listinfo/varnish-misc
