Janne,
Thanks for your advice. I'll have a try. :)
On 2023/3/16 15:00, Janne Johansson wrote:
Den tors 16 mars 2023 kl 06:42 skrev Norman <norman.kern@xxxxxxx>:
Janne,
Thanks for your reply. To reduce the cost of recovering OSDs while
WAL/DB device is down, maybe I have no
choice but add more WAL/DB devices.
We do run one ssd-or-nvme for several OSD hdd drives and have not seen
this as a problem in itself. For us, hdds still break down more often
than the flash drives, though we choose flash drives with DWPD > 3 to
make sure it can sustain a lot of writes over time. If you use (please
don't!) cheap consumer ssds or whatever, then I think they will break
down as often as spin drives, and having less or one such per hdd
would be a wiser choice.
Still, we try to build our clusters so we can handle a whole box
falling off, which means 8 or 12 hdd drives are gone at the same time,
so compared to this, having a single SSD take out 3-4-5 OSDs is not a
complete disaster and well within the expected margins.
One has to take into account that boxes will crash, drives will fail,
processes will crash sometimes and so on, this is why we build
clusters, so that other units can help share the load when (not if) it
happens.
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