For Bluestore I can't find any documentation or discussions about drive write cache, while I can imagine that revisiting this subject might be necessary.
For our cluster specifically, we use HP gen 9 with a b140i controller where disks are directly attached (i.e., not RAID). Often with the Linux kernel, controllers automatically enable drive write cache for directly attached harddisks since this *should* be safe as long as harddisks correctly adhere to flush semantics . In the case of the b140i controller; I can confirm with `hdparm -W /dev/sdx` that drive write cache is *not* enabled by default.
So my main two questions are:
1. Did anybody do extensive testing, with luminous in combination with drive write cache enabled, or at least elaborate on the subject.
2. Depending on item 1., could and should I enable drive write cache for the disks attached to a HP b140i controller.
Thanks!
Hans
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