Hi Yaniv, Thanks for the quick response. I forget to mention I am testing the writing performance, not reading. In this case, would the client cache hit rate still be a big issue?
I'll use fio to run my test once again, thanks for the suggestion. Thanks, Qing On Tue, Jul 21, 2020 at 2:38 PM Yaniv Kaul <yk...@redhat.com> wrote: > > > On Tue, 21 Jul 2020, 21:30 Qing Wang <q...@g.clemson.edu> wrote: > >> Hi, >> >> I am trying to test Gluster linear scale-out performance by adding more >> storage server/bricks, and measure the storage I/O performance. To vary the >> storage server number, I create several "stripe" volumes that contain 2 >> brick servers, 3 brick servers, 4 brick servers, and so on. On gluster >> client side, I used "dd if=/dev/zero of=/mnt/glusterfs/dns_test_data_26g >> bs=1M count=26000" to create 26G data (or larger size), and those data will >> be distributed to the corresponding gluster servers (each has gluster brick >> on it) and "dd" returns the final I/O throughput. The Internet is 40G >> infiniband, although I didn't do any specific configurations to use >> advanced features. >> > > Your dd command is inaccurate, as it'll hit the client cache. It is also > single threaded. I suggest switching to fio. > Y. > > >> What confuses me is that the storage I/O seems not to relate to the >> number of storage nodes, but Gluster documents said it should be linear >> scaling. For example, when "write-behind" is on, and when Infiniband "jumbo >> frame" (connected mode) is on, I can get ~800 MB/sec reported by "dd", no >> matter I have 2 brick servers or 8 brick servers -- for 2 server case, each >> server can have ~400 MB/sec; for 4 server case, each server can have >> ~200MB/sec. That said, each server I/O does aggregate to the final storage >> I/O (800 MB/sec), but this is not "linear scale-out". >> >> Can somebody help me to understand why this is the case? I certainly can >> have some misunderstanding/misconfiguration here. Please correct me if I >> do, thanks! >> >> Best, >> Qing >> ________ >> >> >> >> Community Meeting Calendar: >> >> Schedule - >> Every 2nd and 4th Tuesday at 14:30 IST / 09:00 UTC >> Bridge: https://bluejeans.com/441850968 >> >> Gluster-users mailing list >> Gluster-users@gluster.org >> https://lists.gluster.org/mailman/listinfo/gluster-users >> >
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