Dear Mark. Thank you very much for all of this information. I learned a lot! In particular that I need to learn more about pinning. In the end, I want to run the whole thing in production with real world workloads. My main aim in running the benchmark is to ensure that my hardware and OS is correctly configured (I already found some configuration issues in my switches on the way with lack of balancing between LAG interconnects and using layer 3+4 in creatikg my bonds, particularities of Dell VLTi and needing unique VLT IDs...). Also, it will be interesting to see how and whether things will turn out to be after the cluster has run for a year. As far as I can see, network and OS configuration is sane. Ceph configuration appears to be not too far off something that I could hand to my users. I will try to play a bit more on the pinning and meta data tuning. Best wishes, Manuel Mark Nelson <mnelson@xxxxxxxxxx> schrieb am Do., 1. Dez. 2022, 20:19: > Hi Manuel, > > > I did the IO500 runs back in 2020 and wrote the cephfs aiori backend for > IOR/mdtest. Not sure about the segfault, it's been a while since I've > touched that code. It was working the last time I used it. :D Having > said that, I don't think that's your issue. The userland backend > helped work around an issue where I wasn't able to exceed about 3GB/s > per host with the kernel client and thus couldn't hit more than about > 30GB/s in the easy tests on a 10 node setup. I think Jeff Layton might > have fixed that issue when he improved the locking code in the kernel a > while back and it appears you are getting good results with the kernel > client in the easy tests. I don't recall the userland backend > performing much different than the kernel client in the other tests. > Instead I would recommend looking at each test individually: > > > ior-easy-write (and read): > > Each process gets it's own file, large aligned IO. Pretty easy for the > MDS and the rest of Ceph to handle. You get better results overall than > I did! These are the tests we typically do best on out of the box. > > > mdtest-easy-write (and stat/delete): > > Each process gets it's own directory writing out zero sized files. The > trick to getting good performance here is to use ephemeral pinning on > the parent test directory. Even better would be to use static round > robin pinning for each rank's sub-directory. Sadly that violates the > rules now and we haven't implemented a way to do this with a single > parent level xattr (though it would be pretty easy which makes the rule > not to touch the subdirs kind of silly imho). I was able to achieve up > to around 10K IOPs per MDS, with the highest achieved score around > 400-500K IOPS with 80 MDSes (but that configuration was suboptimal for > other tests). Ephemeral pinning is ok, but you need enough directories > to avoid "clumpy" distribution across MDSes. At ~320 > processes/directories and 40 MDSes I was seeing about half the > performance vs doing perfect round-robin pinning of the individual > process directories. Well, with one exception: When doing manual > pinning, it's better to exclude the authoritative MDS for the parent > directory (or perhaps just give it fewer directories than the others) > since it's also doing other work and ends up lagging behind slowing the > whole benchmark down. Having said that, this is one of the easier tests > to improve so long as you use some kind of reasonable pinning strategy > with multiple MDSes. > > > ior-hard-write (and read): > > Small unaligned IO to a single shared file. I think it's ~47K IOs. > This is rough to improve without code changes imho. I remember the > results being highly variable in my tests, and it took multiple runs to > get a high score. I don't remember exactly what I had to tweak here, > but as opposed to the easy tests you are likely heavily latency bound > even with 47K IOs. I expect you are going to be slamming a single OSD > (and PG!) over and over from multiple clients and constrained by how > quickly you can get those IOs replicated (for writes when rep > 1) and > locks acquired/released (in all cases). I'm guessing that ensuring the > lowest possible per-OSD latency and highest per-OSD throughput is > probably a big win here. Not sure what on the CephFS side might be > playing a role, but I imagine caps and file level locking might matter. > You can imagine that a system that let you just dump IO as a log-append > straight to disk with some kind of clever scheme to avoid file based > locking would do better here. > > > mdtest-hard-write (and stat/delete): > > All processes writing 3901 byte files to a single directory. dirfrag > splitting and exporting is a huge bottleneck. The balancing code in the > MDS can basically DDOS itself to the point where in a 30s (or even a 5 > minute!) test you never actually export anything to other MDSes. You > both end up servicing all requests on the authoritative MDS while > simultaneously doing a bunch of work trying and failing to acquire locks > to do the dirfrag exports. If you do manage to actually get dirfrags > onto other MDSes it can lead to performance improvements, but even then > there are cyclical near-stalls in throughput that tank performance, > likely related to further splitting and attempting to export dirfrags. > As the subtree map grows, journal writes on the authoritative MDS for > the parent directory become consuming. If I recall it took a lot of > screwing around with MDS and client counts to get a good result, and > luck played a role too like in the ior-hard tests. It was easy to do > worse than just pinning to a single MDS. FWIW, I usually saw higher > aggregate performance with longer running tests than I did with lower > running tests. > > > find: > > Find a subset of the files created in the 4 above tests. A bit of a > ridiculous test frankly. Results are highly dependent on the amount of > files created in the easy vs hard mdtest cases above. The higher you > skew toward easy tests, the better the find number becomes. They should > have separate find tests for easy mdtest and hard mdtest files and just > ignore IOR entirely. > > > FWIW there are some long-running efforts to improve some of the > bottlenecks I mentioned, especially during subtree map journal writes. > Zheng had a PR a while back but it was fairly complex and never got > merged. I believe Patrick is taking a crack at it now using a different > approach. FWIW, there are also a couple of good links from Matt > Rásó-Barnett (Cambridge) and Glenn Lockwood (Formerly at NERSC, now > heading up HPC IO strategy at Microsoft) that talk about some of IO500 > tests and the good and bad here: > > > https://www.eofs.eu/_media/events/lad19/03_matt_raso-barnett-io500-cambridge.pdf > > https://www.glennklockwood.com/benchmarks/io500.html > > > Mark > > > On 12/1/22 01:26, Manuel Holtgrewe wrote: > > Dear all, > > > > I am currently creating a CephFS setup for a HPC setting. I have a Ceph > > v17.2.5 Cluster on Rocky Linux 8.7 (Kernel 4.18.0-425.3.1.el8.x86_64) > > deployed with cephadm. I have 10 Ceph nodes with 2x100GbE LAG > interconnect > > and 36 client nodes with 2x25GbE LAG interconnect. We have Dell NOS10 > > switches deployed in VLT pairs. Overall, the network topology looks as > > follows. > > > > 36 clients -- switch pair -- switch pair -- switch-pair -- 10 Ceph nodes > > > > The switch pairs are each connected with 8x100GbE LAG overall. Thus, the > > theoretic network limit is ~80GB/sec. > > > > The client nodes also run Rocky Linux 8 and have 2x Intel(R) Xeon(R) Gold > > 6240R CPU @ 2.40GHz CPUs. The Ceph nodes have 1x AMD EPYC 7413 24-Core > > Processor and 250GB of RAM. All processors have hyperthreading enabled. I > > have followed the guidance by Croit [1] and done the obvious hardware > > tuning (configured the BIOS to make the OS do the power control, setup > the > > network with MTU 9000. I have deployed 3 MDS per server and have 20 > active > > overall. > > > > The Ceph cluster nodes have 10x enterprise NVMEs each (all branded as > "Dell > > enterprise disks"), 8 older nodes (last year) have "Dell Ent NVMe v2 AGN > RI > > U.2 15.36TB" which are Samsung disks, 2 newer nodes (just delivered) have > > "Dell Ent NVMe CM6 RI 15.36TB" which are Kioxia disks. Interestingly, the > > Kioxia disks show about 50% higher IOPs in the 4-processor fio test that > > Croit suggests. > > > > I'm running the IO500 benchmark with 10 processes each on the clients. I > > have pools setup with rep-1, rep-2, rep-3, and EC 8+2 and run the > > benchmarks. > > > > So far, I have run "only" short tests with IO500 wall clock time of 30 > > secs. Good results for me are that I see "ior-easy-write" results of > > 80GiB/sec so the Ceph cluster is able to saturate the switch network > > interconnects. Bad results for me are that I cannot replicate the IO500 > > results from Red Hat in 2020. > > > > Below are the results that I get on the rep-1 pool. > > > > ``` > > IO500 version io500-sc22_v2 (standard) > > [RESULT] ior-easy-write 78.772830 GiB/s : time 97.098 seconds > > [INVALID] > > [RESULT] mdtest-easy-write 37.375945 kIOPS : time 870.934 > seconds > > [ ] timestamp 0.000000 kIOPS : time 0.000 seconds > > [RESULT] ior-hard-write 2.242241 GiB/s : time 35.431 seconds > > [INVALID] > > [RESULT] mdtest-hard-write 2.575028 kIOPS : time 57.697 seconds > > [INVALID] > > [RESULT] find 1072.770588 kIOPS : time 30.441 seconds > > [RESULT] ior-easy-read 64.118118 GiB/s : time 118.982 > seconds > > [RESULT] mdtest-easy-stat 154.903631 kIOPS : time 210.887 > seconds > > [RESULT] ior-hard-read 4.285418 GiB/s : time 18.474 seconds > > [RESULT] mdtest-hard-stat 40.126159 kIOPS : time 4.646 seconds > > [RESULT] mdtest-easy-delete 39.296673 kIOPS : time 839.509 > seconds > > [RESULT] mdtest-hard-read 17.161306 kIOPS : time 9.505 seconds > > [RESULT] mdtest-hard-delete 4.771440 kIOPS : time 31.931 seconds > > [SCORE ] Bandwidth 14.842537 GiB/s : IOPS 34.623082 kiops : TOTAL > 22.669239 > > [INVALID] > > ``` > > > > I wonder whether I missed any tuning parameters or other "secret sauce" > > that enabled the results from [2]: > > > > ``` > > [RESULT] BW phase 1 ior_easy_write 36.255 > GiB/s > > : time 387.94 seconds > > [RESULT] IOPS phase 1 mdtest_easy_write 191.980 > kiops > > : time 450.05 seconds > > [RESULT] BW phase 2 ior_hard_write 9.137 > GiB/s > > : time 301.21 seconds > > [RESULT] IOPS phase 2 mdtest_hard_write 17.187 > kiops > > : time 393.55 seconds > > [RESULT] IOPS phase 3 find 965.790 > kiops > > : time 96.46 seconds > > [RESULT] BW phase 3 ior_easy_read 75.621 > GiB/s > > : time 185.75 seconds > > [RESULT] IOPS phase 4 mdtest_easy_stat 903.112 > kiops > > : time 95.67 seconds > > [RESULT] BW phase 4 ior_hard_read 19.080 > GiB/s > > : time 144.22 seconds > > [RESULT] IOPS phase 5 mdtest_hard_stat 97.399 > kiops > > : time 69.44 seconds > > [RESULT] IOPS phase 6 mdtest_easy_delete 123.455 > kiops > > : time 699.85 seconds > > [RESULT] IOPS phase 7 mdtest_hard_read 87.512 > kiops > > : time 77.29 seconds > > [RESULT] IOPS phase 8 mdtest_hard_delete 18.814 > kiops > > : time 390.91 seconds > > [SCORE] Bandwidth 26.2933 GiB/s : IOPS 124.297 kiops : TOTAL 57.168 > > ``` > > > > It looks like my results are more in the same order as the SUSE results > > from 2019 [3]. > > > > ``` > > [RESULT] BW phase 1 ior_easy_write 16.072 > GB/s : > > time 347.39 seconds > > [RESULT] IOPS phase 1 mdtest_easy_write 32.822 > kiops > > : time 365.67 seconds > > [RESULT] BW phase 2 ior_hard_write 1.572 > GB/s : > > time 359.20 seconds > > [RESULT] IOPS phase 2 mdtest_hard_write 12.917 > kiops > > : time 317.70 seconds > > [RESULT] IOPS phase 3 find 250.500 > kiops > > : time 64.28 seconds > > [RESULT] BW phase 3 ior_easy_read 9.139 > GB/s : > > time 600.48 seconds > > [RESULT] IOPS phase 4 mdtest_easy_stat 127.919 > kiops > > : time 93.82 seconds > > [RESULT] BW phase 4 ior_hard_read 4.698 > GB/s : > > time 120.17 seconds > > [RESULT] IOPS phase 5 mdtest_hard_stat 68.791 > kiops > > : time 59.65 seconds > > [RESULT] IOPS phase 6 mdtest_easy_delete 20.845 > kiops > > : time 575.70 seconds > > [RESULT] IOPS phase 7 mdtest_hard_read 41.640 > kiops > > : time 98.55 seconds > > [RESULT] IOPS phase 8 mdtest_hard_delete 6.224 > kiops > > : time 660.50 seconds > > [SCORE] Bandwidth 5.73936 GB/s : IOPS 38.7169 kiops : TOTAL 14.9067 > > ``` > > > > One difference I could find is that the Red Hat results use the CEPHFS > > backend of IO500 (that I cannot get to work properly because of a crash > > "Caught signal 11 (Segmentation fault: address not mapped to object at > > address (nil))" in libucs.so. SUSE used the POSIX backend. > > > > Changing from 1 OSD server per NVME to 2 did not help too much either. > > > > Maybe someone on the list has an idea for something else to try? > > > > Oh, in case anyone is interested, here are some results using the rep-2, > > rep-3, and ec-8-2 pool. > > > > ``` > > *** pool=rep-2 NP=360 *** > > IO500 version io500-sc22_v2 (standard) > > [RESULT] ior-easy-write 39.613736 GiB/s : time 153.508 > seconds > > [INVALID] > > [RESULT] mdtest-easy-write 13.932462 kIOPS : time 38.119 seconds > > [INVALID] > > [ ] timestamp 0.000000 kIOPS : time 0.000 seconds > > [RESULT] ior-hard-write 1.809117 GiB/s : time 39.019 seconds > > [INVALID] > > [RESULT] mdtest-hard-write 4.925225 kIOPS : time 37.654 seconds > > [INVALID] > > [RESULT] find 69.063353 kIOPS : time 9.042 seconds > > [RESULT] ior-easy-read 59.503973 GiB/s : time 102.166 > seconds > > [RESULT] mdtest-easy-stat 143.589003 kIOPS : time 4.097 seconds > > [RESULT] ior-hard-read 4.104325 GiB/s : time 14.868 seconds > > [RESULT] mdtest-hard-stat 156.252159 kIOPS : time 2.204 seconds > > [RESULT] mdtest-easy-delete 35.312782 kIOPS : time 14.249 seconds > > [RESULT] mdtest-hard-read 67.097465 kIOPS : time 3.739 seconds > > [RESULT] mdtest-hard-delete 11.018869 kIOPS : time 18.060 seconds > > [SCORE ] Bandwidth 11.502045 GiB/s : IOPS 35.927582 kiops : TOTAL > 20.328322 > > [INVALID] > > > > > > *** pool=rep-3 NP=360 *** > > IO500 version io500-sc22_v2 (standard) > > [RESULT] ior-easy-write 27.481332 GiB/s : time 204.973 > seconds > > [INVALID] > > [RESULT] mdtest-easy-write 27.699574 kIOPS : time 1502.596 > seconds > > [ ] timestamp 0.000000 kIOPS : time 0.000 seconds > > [RESULT] ior-hard-write 1.352186 GiB/s : time 38.273 seconds > > [INVALID] > > [RESULT] mdtest-hard-write 3.024279 kIOPS : time 48.923 seconds > > [INVALID] > > [RESULT] find 777.440295 kIOPS : time 53.684 seconds > > [RESULT] ior-easy-read 58.686272 GiB/s : time 95.992 seconds > > [RESULT] mdtest-easy-stat 156.499256 kIOPS : time 266.755 > seconds > > [RESULT] ior-hard-read 4.095575 GiB/s : time 12.649 seconds > > [RESULT] mdtest-hard-stat 62.831560 kIOPS : time 3.318 seconds > > [RESULT] mdtest-easy-delete 25.909017 kIOPS : time 1606.960 > seconds > > [RESULT] mdtest-hard-read 16.586529 kIOPS : time 9.735 seconds > > [RESULT] mdtest-hard-delete 9.093536 kIOPS : time 18.615 seconds > > [SCORE ] Bandwidth 9.721458 GiB/s : IOPS 35.464915 kiops : TOTAL > 18.568002 > > [INVALID] > > > > > > *** pool=ec-8-2 NP=360 *** > > IO500 version io500-sc22_v2 (standard) > > [RESULT] ior-easy-write 40.480456 GiB/s : time 151.451 > seconds > > [INVALID] > > [RESULT] mdtest-easy-write 32.507690 kIOPS : time 444.424 > seconds > > [ ] timestamp 0.000000 kIOPS : time 0.000 seconds > > [RESULT] ior-hard-write 0.570092 GiB/s : time 35.986 seconds > > [INVALID] > > [RESULT] mdtest-hard-write 3.287144 kIOPS : time 40.114 seconds > > [INVALID] > > [RESULT] find 1779.068273 kIOPS : time 8.177 seconds > > [RESULT] ior-easy-read 56.463968 GiB/s : time 108.661 > seconds > > [RESULT] mdtest-easy-stat 179.334380 kIOPS : time 81.380 seconds > > [RESULT] ior-hard-read 1.957840 GiB/s : time 10.484 seconds > > [RESULT] mdtest-hard-stat 92.430508 kIOPS : time 2.402 seconds > > [RESULT] mdtest-easy-delete 29.549239 kIOPS : time 489.285 > seconds > > [RESULT] mdtest-hard-read 26.989114 kIOPS : time 5.770 seconds > > [RESULT] mdtest-hard-delete 26.500674 kIOPS : time 6.038 seconds > > [SCORE ] Bandwidth 7.106974 GiB/s : IOPS 53.448254 kiops : TOTAL > 19.489879 > > [INVALID] > > ``` > > > > Best wishes, > > Manuel > > > > [1] https://croit.io/blog/ceph-performance-test-and-optimization > > [2] https://io500.org/submissions/view/82 > > [3] https://io500.org/submissions/view/141 > > _______________________________________________ > > ceph-users mailing list -- ceph-users@xxxxxxx > > To unsubscribe send an email to ceph-users-leave@xxxxxxx > > > > _______________________________________________ > ceph-users mailing list -- ceph-users@xxxxxxx > To unsubscribe send an email to ceph-users-leave@xxxxxxx > _______________________________________________ ceph-users mailing list -- ceph-users@xxxxxxx To unsubscribe send an email to ceph-users-leave@xxxxxxx
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