Il giorno sab 15 apr 2023 alle ore 11:10 Marco Gaiarin < gaio@xxxxxxxxxxxxxxxxx> ha scritto: > > Sorry, i'm a bit puzzled here. > > Matthias suggest to enable write cache, you suggest to disble it... or i'm > cache-confused?! ;-) > > > > There is a cache in each disk, and a cache in the controller. The disk cache is: - volatile, if power goes away content is lost (some nvme disks have PLP that is a capacitor so cache in this case is not volatile) - ecc only in sas disks - needed for ssd (most ssd wear leveling algorithms have problems without cache) The controller cache: - is not volatile, if the controller has BBU - usually has ecc ram Usually when you have a BBU raid controller you disable single disks cache and keep only controller cache which is protected by battery. Ceph experts tell you to disable controller cache and raid but no one was able to tell me what to do with disk cache: - if you disable it disk performance becomes very slow and you risk problems in ssd - if you enable it disk will lose content if power goes away. Now ceph experts will tell you to buy only disks with PLP to solve the problem... but hdds do not have plp (if you find an hdd with plp tell me I will buy it) _______________________________________________ ceph-users mailing list -- ceph-users@xxxxxxx To unsubscribe send an email to ceph-users-leave@xxxxxxx
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