Lines Matching +full:always +full:- +full:wait +full:- +full:for +full:- +full:ack
1 .. SPDX-License-Identifier: GPL-2.0-only
3 dm-vdo
6 The dm-vdo (virtual data optimizer) device mapper target provides
7 block-level deduplication, compression, and thin provisioning. As a device
20 https://github.com/dm-vdo/vdo/
25 enter or come up in read-only mode. Because read-only mode is indicative of
26 data-loss, a positive action must be taken to bring vdo out of read-only
28 prepare a read-only vdo to exit read-only mode. After running this tool,
34 inspect a vdo target's on-disk metadata. Fortunately, these tools are
35 rarely needed except by dm-vdo developers.
40 Each vdo volume reserves 3GB of space for metadata, or more depending on
43 requirements. An estimation of the space saved for a specific dataset can
46 https://github.com/dm-vdo/vdoestimator/
52 ----------
77 of 4096-byte blocks. Must match the current size of the vdo
81 The minimum I/O size for this vdo volume to accept, in
86 The size of the block map cache, as a number of 4096-byte
88 If the logical thread count is non-zero, the cache size
100 --------------------
110 values are non-zero, all of them must be non-zero.
112 ack:
131 The number of threads used to do CPU-intensive work, such
135 The number of threads used to manage data comparisons for
146 underlying storage device. At format time, a slab size for
154 The maximum size of discard bio accepted, in 4096-byte
156 into 4096-byte blocks, and processed up to 2048 at a time.
159 4096-byte blocks in a single bio, and are limited to 1500
161 performance, at the cost of increased latency for the
174 -------------------
176 A modified table may be loaded into a running, non-suspended vdo volume.
185 least 32832 4096-byte blocks if at all, and must not exceed the size of the
193 Start a previously-formatted vdo volume with 1 GB logical space and 1 GB
194 physical space, storing to /dev/dm-1 which has more than 1 GB of space.
198 dmsetup create vdo0 --table \
199 "0 2097152 vdo V4 /dev/dm-1 262144 4096 32768 16380"
205 dmsetup reload vdo0 --table \
206 "0 8388608 vdo V4 /dev/dm-1 262144 4096 32768 16380"
213 dmsetup reload vdo0 --table \
214 "0 8388608 vdo V4 /dev/dm-1 524288 4096 32768 16380"
221 dmsetup reload vdo0 --table \
222 "0 10485760 vdo V4 /dev/dm-1 786432 4096 32768 16380 maxDiscard 8"
236 dmsetup create vdo1 --table \
237 "0 10485760 vdo V4 /dev/dm-1 786432 512 65550 5000 hash 1 logical 3 physical 2"
240 --------
245 dmsetup message <target-name> 0 <message-name> <message-parameters>
261 not always safe to run, so it should only be used to debug
267 vdo: Most of the structures managing on-disk data
273 dump-on-shutdown:
278 ------
292 'read-only' (an error has occurred that forces the vdo
297 values may be 'recovering' or '-' which indicates not
324 - 1.15 MB of RAM for each 1 MB of configured block map cache size. The
326 - 1.6 MB of RAM for each 1 TB of logical space.
327 - 268 MB of RAM for each 1 TB of physical storage managed by the volume.
330 size of the deduplication window. For dense indexes, the index requires 1
331 GB of RAM per 1 TB of window. For sparse indexes, the index requires 1 GB
342 Run-time Usage
345 When using dm-vdo, it is important to be aware of the ways in which its
348 - There is no guarantee that over-writes of existing blocks will succeed.
349 Because the underlying storage may be multiply referenced, over-writing
353 - When blocks are no longer in use, sending a discard request for those
354 blocks lets the vdo release references for those blocks. If the vdo is
357 duplicate blocks, no discard request for any given logical block is
360 - Assuming the underlying storage properly implements flush requests, vdo
364 - Each write to a vdo target entails a significant amount of processing.
381 service a request for any logical address, a vdo must load the portion of
386 up proportionally for larger working sets.
397 reorder I/O requests for performance benefit, but also that each I/O
398 request has to wait longer before being submitted.
400 Bio acknowledgment threads are used for finishing I/O requests. This is
404 bios have CPU-heavy callbacks.
406 CPU threads are used for hashing and for compression; in workloads with
411 threads are comparison of 4096-byte data blocks. In most cases, a single