> there is an option set in the controller "Block SSD Write Disk Cache Change = Yes" which does not permit to deactivate the ssd cache. I could not find any solution in google for this controller (LSI MegaRAID SAS 9271-8i) to change this setting. I assume you are referencing this parameter? storcli /c0/v0 set ssdcaching=<on|off> If so, this is for CacheCade, which is LSI's cache tiering solution, which should both be off and not in use for ceph. Single thread and single iodepth benchmarks will tend to be underwhelming. Ceph shines with aggregate performance from lots of clients. And in an odd twist of fate, I typically see better performance on RBD for random benchmarks rather than sequential benchmarks, as it distributes the load across more OSD's. Might also help others offer some pointers for tuning if you describe the pool/application a bit more. Ie RBD vs cephfs vs RGW, 3x replicated vs EC, etc. At least things are trending in a positive direction. Reed > On Sep 1, 2020, at 4:21 PM, VELARTIS Philipp Dürhammer <p.duerhammer@xxxxxxxxxxx> wrote: > > Thank you. I was working in this direction. The situation is a lot better. But I think I can get still far better. > > I could set the controller to writethrough, direct and no read ahead for the ssds. > But I cannot disable the pdcache ☹ there is an option set in the controller "Block SSD Write Disk Cache Change = Yes" which does not permit to deactivate the ssd cache. I could not find any solution in google for this controller (LSI MegaRAID SAS 9271-8i) to change this setting. > > I don’t know how much performance gain it will be to deactivate the ssd cache. At least the micron 5200max has capacitor so I hope it is safe for data loss in case if power failure. I wrote a request to lsi / Broadcom if they know how I can change this setting. This is really annyoing. > > I will check the cpu power settings. I rode also somewhere it can improve iops a lot. (if its bad set) > > At the moment I get 600iops 4k random write 1 thread and 1 iodepth. I get 40K - 4k random iops for some instances with 32iodepth. Its not the world but a lot better then before. Read around 100k iops. For 16 ssd's and 2 x dual 10G nic. > > I was reading that good tunings and hardware config can get more then 2000 iops on single thread out of the ssds. I know thet ceph does not shine with single thread. But 600 iops is not very much... > > philipp > > -----Ursprüngliche Nachricht----- > Von: Reed Dier <reed.dier@xxxxxxxxxxx> > Gesendet: Dienstag, 01. September 2020 22:37 > An: VELARTIS Philipp Dürhammer <p.duerhammer@xxxxxxxxxxx> > Cc: ceph-users@xxxxxxx > Betreff: Re: Can 16 server grade ssd's be slower then 60 hdds? (no extra journals) > > If using storcli/perccli for manipulating the LSI controller, you can disable the on-disk write cache with: > storcli /cx/vx set pdcache=off > > You can also ensure that you turn off write caching at the controller level with > storcli /cx/vx set iopolicy=direct > storcli /cx/vx set wrcache=wt > > You can also tweak the readahead value for the vd if you want, though with an ssd, I don't think it will be much of an issue. > storcli /cx/vx set rdcache=nora > > I'm sure the megacli alternatives are available with some quick searches. > > May also want to check your c-states and p-states to make sure there isn't any aggressive power saving features getting in the way. > > Reed > >> On Aug 31, 2020, at 7:44 AM, VELARTIS Philipp Dürhammer <p.duerhammer@xxxxxxxxxxx> wrote: >> >> We have older LSi Raid controller with no HBA/JBOD option. So we expose the single disks as raid0 devices. Ceph should not be aware of cache status? >> But digging deeper in to it it seems that 1 out of 4 serves is performing a lot better and has super low commit/applay rates while the other have a lot mor (20+) on heavy writes. This just applys fore the ssd. For the hdds I cant see a difference... >> >> -----Ursprüngliche Nachricht----- >> Von: Frank Schilder <frans@xxxxxx> >> Gesendet: Montag, 31. August 2020 13:19 >> An: VELARTIS Philipp Dürhammer <p.duerhammer@xxxxxxxxxxx>; 'ceph-users@xxxxxxx' <ceph-users@xxxxxxx> >> Betreff: Re: Can 16 server grade ssd's be slower then 60 hdds? (no extra journals) >> >> Yes, they can - if volatile write cache is not disabled. There are many threads on this, also recent. Search for "disable write cache" and/or "disable volatile write cache". >> >> You will also find different methods of doing this automatically. >> >> Best regards, >> ================= >> Frank Schilder >> AIT Risø Campus >> Bygning 109, rum S14 >> >> ________________________________________ >> From: VELARTIS Philipp Dürhammer <p.duerhammer@xxxxxxxxxxx> >> Sent: 31 August 2020 13:02:45 >> To: 'ceph-users@xxxxxxx' >> Subject: Can 16 server grade ssd's be slower then 60 hdds? (no extra journals) >> >> I have a productive 60 osd's cluster. No extra Journals. Its performing okay. Now I added an extra ssd Pool with 16 Micron 5100 MAX. And the performance is little slower or equal to the 60 hdd pool. 4K random as also sequential reads. All on dedicated 2 times 10G Network. HDDS are still on filestore. SSD on bluestore. Ceph Luminous. >> What should be possible 16 ssd's vs. 60 hhd's no extra journals? >> >> _______________________________________________ >> 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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