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doc: update some of the outdated cache tiering doc

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Signed-off-by: Zhiqiang Wang <zhiqiang.wang@intel.com>
This commit is contained in:
Zhiqiang Wang 2015-08-20 10:58:45 +08:00
parent de00f6d0df
commit d5a56c497a
2 changed files with 10 additions and 11 deletions
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13
doc/dev/cache-pool.rst
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@ -105,13 +105,7 @@ The hit_set_count and hit_set_period define how much time each HitSet
should cover, and how many such HitSets to store. Binning accesses
over time allows Ceph to independently determine whether an object was
accessed at least once and whether it was accessed more than once over
some time period ("age" vs "temperature"). Note that the longer the
period and the higher the count the more RAM will be consumed by the
ceph-osd process. In particular, when the agent is active to flush or
evict cache objects, all hit_set_count HitSets are loaded into RAM.
Currently there is minimal benefit for hit_set_count > 1 since the
agent does not yet act intelligently on that information.
some time period ("age" vs "temperature").
The ``min_read_recency_for_promote`` defines how many HitSets to check for the
existence of an object when handling a read operation. The checking result is
@ -124,6 +118,11 @@ found in any of the most recent ``min_read_recency_for_promote`` HitSets. ::
ceph osd pool set {cachepool} min_read_recency_for_promote 1
Note that the longer the ``hit_set_period`` and the higher the
``min_read_recency_for_promote`` the more RAM will be consumed by the ceph-osd
process. In particular, when the agent is active to flush or evict cache objects,
all hit_set_count HitSets are loaded into RAM.
Cache mode
~~~~~~~~~~

8
doc/rados/operations/cache-tiering.rst
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@ -197,10 +197,10 @@ found in any of the most recent ``min_read_recency_for_promote`` HitSets. ::
ceph osd pool set {cachepool} min_read_recency_for_promote 1
.. note:: The longer the period and the higher the count, the more RAM the
``ceph-osd`` daemon consumes. In particular, when the agent is active to
flush or evict cache objects, all ``hit_set_count`` HitSets are loaded
into RAM.
.. note:: The longer the period and the higher the min_read_recency_for_promote,
the more RAM the ``ceph-osd`` daemon consumes. In particular, when the agent
is active to flush or evict cache objects, all ``hit_set_count`` HitSets are
loaded into RAM.
Cache Sizing