[Bug 1758697] Re: support advanced bcache tuning flags

[John]

Auto-closed: no activity for over 731 days.

** Changed in: charm-ceph-osd
       Status: Triaged => Expired

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Title:
  support advanced bcache tuning flags

Status in Ceph OSD Charm:
  Expired
Status in OpenStack Nova Compute Charm:
  Triaged
Status in curtin:
  Triaged

Bug description:
  It would be nice if curin supported some bcache tuning flags in
  addition to the current cache_mode settings.

  For example, a config flag for sequential_cutoff would be nice to have
  to maximize the usage of SSD.

  >  - Bad performance, or traffic not going to the SSD that you'd expect
  > 
  >    By default, bcache doesn't cache everything. It tries to skip sequential IO -
  >    because you really want to be caching the random IO, and if you copy a 10
  >    gigabyte file you probably don't want that pushing 10 gigabytes of randomly
  >    accessed data out of your cache.
  > 
  >    But if you want to benchmark reads from cache, and you start out with fio
  >    writing an 8 gigabyte test file - so you want to disable that::
  > 
  > 	# echo 0 > /sys/block/bcache0/bcache/sequential_cutoff

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