Lines Matching refs:cache
4 dm-cache is a device mapper target written by Joe Thornber, Heinz
33 may be out of date or kept in sync with the copy on the cache device
47 2. A cache device - the small, fast one.
49 3. A small metadata device - records which blocks are in the cache,
51 This information could be put on the cache device, but having it
54 be used by a single cache device.
60 is configurable when you first create the cache. Typically we've been
66 getting hit a lot, yet the whole block will be promoted to the cache.
67 So large block sizes are bad because they waste cache space. And small
74 The cache has three operating modes: writeback, writethrough and
78 cached will go only to the cache and the block will be marked dirty in
82 complete until it has hit both the origin and cache devices. Clean
85 If passthrough is selected, useful when the cache contents are not known
87 the origin device (all reads miss the cache) and all writes are
88 forwarded to the origin device; additionally, write hits cause cache
89 block invalidates. To enable passthrough mode the cache must be clean.
90 Passthrough mode allows a cache device to be activated without having to
92 the cache will gradually cool as writes take place. If the coherency of
93 the cache can later be verified, or established through use of the
94 "invalidate_cblocks" message, the cache device can be transitioned to
95 writethrough or writeback mode while still warm. Otherwise, the cache
100 dirty blocks in a cache. Useful for decommissioning a cache or when
101 shrinking a cache. Shrinking the cache's fast device requires all cache
102 blocks, in the area of the cache being removed, to be clean. If the
103 area being removed from the cache still contains dirty blocks the resize
105 cache's fast device until the cache is clean. This is of particular
107 modes already maintain a clean cache. Future support to partially clean
108 the cache, above a specified threshold, will allow for keeping the cache
114 Migrating data between the origin and cache device uses bandwidth.
129 means the cache behaves like a physical disk that has a volatile write
130 cache. If power is lost you may lose some recent writes. The metadata
133 The 'dirty' state for a cache block changes far too frequently for us
136 system crashes all cache blocks will be assumed dirty when restarted.
141 Policy plug-ins can store a chunk of data per cache block. It's up to
147 uses this facility to store the hit count of the cache blocks. If
148 there's a crash this information will be lost, which means the cache
158 messages are used. Refer to cache-policies.txt.
167 from the cache blocks. This is because we need to track the discard
169 which is just for the smaller cache device).
177 cache <metadata dev> <cache dev> <origin dev> <block size>
182 cache dev : fast device holding cached data blocks
184 block size : cache unit size in sectors
194 See cache-policies.txt for details.
197 writethrough : write through caching that prohibits cache block
200 back cache block contents later for performance reasons,
203 passthrough : a degraded mode useful for various cache coherency
207 block, then the cache block is invalidated.
208 To enable passthrough mode the cache must be clean.
220 <cache block size> <#used cache blocks>/<#total cache blocks>
224 <cache metadata mode>
230 cache block size : Configurable block size for the cache device
232 #used cache blocks : Number of blocks resident in the cache
233 #total cache blocks : Total number of cache blocks
235 to the cache
239 to the cache
243 from the cache
245 the cache
246 #dirty : Number of blocks in the cache that differ
256 cache metadata mode : ro if read-only, rw if read-write
265 cache can be made fully operational again. '-' indicates
283 Invalidation is removing an entry from the cache without writing it
290 invalidation of larger caches. The cache must be in passthrough mode
305 dmsetup create my_cache --table '0 41943040 cache /dev/mapper/metadata \
307 dmsetup create my_cache --table '0 41943040 cache /dev/mapper/metadata \