fio gives me the correct linear scale-out results, and you're right, the storage cache is the root cause that makes the dd measurement results not accurate at all.
Thanks, Qing On Tue, Jul 21, 2020 at 2:53 PM Yaniv Kaul <[email protected]> wrote: > > > On Tue, 21 Jul 2020, 21:43 Qing Wang <[email protected]> wrote: > >> 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? >> > > It's not hitting the storage directly. Since it's also single threaded, it > may also not saturate it. I highly recommend testing properly. > Y. > > >> 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 <[email protected]> wrote: >> >>> >>> >>> On Tue, 21 Jul 2020, 21:30 Qing Wang <[email protected]> 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 >>>> [email protected] >>>> https://lists.gluster.org/mailman/listinfo/gluster-users >>>> >>>
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