Hi, do you want to hear the truth from real experience? Or the myth? The truth is that: - hdd are too slow for ceph, the first time you need to do a rebalance or similar you will discover... - if you want to use hdds do a raid with your controller and use the controller BBU cache (do not consider controllers with hdd cache), and present the raid as one ceph disk. - enabling single hdd write cache (that is not battery protected) is far worse than enabling controller cache (which I assume is always protected by BBU) - anyway the best thing for ceph is to use nvme disks. Mario Il giorno gio 6 apr 2023 alle ore 13:40 Marco Gaiarin < gaio@lilliput.linux.it> ha scritto:
We are testing an experimental Ceph cluster with server and controller at subject.
The controller have not an HBA mode, but only a 'NonRAID' mode, come sort of 'auto RAID0' configuration.
We are using SSD SATA disks (MICRON MTFDDAK480TDT) that perform very well, and SAS HDD disks (SEAGATE ST8000NM014A) that instead perform very bad (particulary, very low IOPS).
There's some hint for disk/controller configuration/optimization?
Thanks.
-- Io credo nella chimica tanto quanto Giulio Cesare credeva nel caso... mi va bene fino a quando non riguarda me :) (Emanuele Pucciarelli)
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