I was talking about on-disk cache, but, yes, the controller cache needs to be disabled too. The first can be done with smartctl or hdparm. Check cache status with something like 'smartctl -g wcache /dev/sda' and disable with something like 'smartctl -s wcache=off /dev/sda'. Controller cache needs to be disabled in the BIOS. By the way, if you can't use pass-through, you should disable controller cache for every disk, including the HDDs. There are cases in the list demonstrating that controller cache enabled can lead to data loss on power outage. As I recommended before, please search the ceph-user list, you will find detailed instructions and also links to explanations and typical benchmarks. Best regards, ================= Frank Schilder AIT Risø Campus Bygning 109, rum S14 ________________________________________ From: VELARTIS Philipp Dürhammer <p.duerhammer@xxxxxxxxxxx> Sent: 31 August 2020 14:44:07 To: Frank Schilder; 'ceph-users@xxxxxxx' Subject: AW: Can 16 server grade ssd's be slower then 60 hdds? (no extra journals) 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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