Lines Matching full:it
11 Corp. starting in 2009. It was first released in 2013 and has been used in
12 production environments ever since. It was made open-source in 2017 after
17 vdo target has a maximum block size of 4K. However, it can achieve
19 reference a single 4K of actual storage. It can achieve compression rates
54 each zone has an implicit lock on the structures it manages for all its
70 have temporal locality. When a duplicate appears, it is more likely that
74 duplicate recent data than it is to duplicate older data and in general,
76 when the index is full, it should cull its oldest records to make space for
80 those savings, vdo does not attempt to find every last duplicate block. It
85 that data on the underlying storage. However, it is not possible to
87 because it is too costly to update the index when a block is over-written
90 storage, or reading and rehashing each block before overwriting it.
95 index as hints, and reads each indicated block to verify that it is indeed
101 open chapter is not finalized until it runs out of space for new records.
102 When the open chapter fills up, it is closed and a new open chapter is
105 Closing a chapter converts it to a different format which is optimized for
113 only a subset of the block name as its key, so it cannot guarantee that an
114 index entry refers to the desired block name. It can only guarantee that if
115 there is a record for this name, it will be on the indicated page. Closed
130 An older record for a block name will no longer be found even though it has
133 say that a record exists for a name. It can only say which chapter would
137 From the viewpoint of a request for a particular block name, it will first
139 the name is new, or which chapter to search. If it returns a chapter, the
141 that the name is new, or which record page to search. Finally, if it is not
157 table, but it is slightly more expensive to look up entries, because a
159 to find the record it needs. The delta index reduces this lookup cost by
167 than that, the index will not be able to find it because the records of the
169 200 GB file to a vdo target and then immediately writes it again, the two
179 later. It is important to consider the expected workload for a vdo target
180 before configuring it.) There are two ways to do this.
212 set of steps to handle the application data, after which it is reset and
257 how full it is. During recovery, each physical zone will attempt to recover
258 at least one slab, stopping whenever it has recovered a slab which has some
266 The block map contains the logical to physical mapping. It can be thought
271 which is unmapped (i.e. it has never been written, or has been discarded),
292 In operation, the block map maintains two caches. It is prohibitive to keep
306 block map page number and the physical block allocated for it. Block map
314 entries themselves are stable. The journal entry and the data write it
323 as vdo has done enough work to guarantee that it can complete the write
325 can be treated as though it is cached in memory. If an application
326 requires data to be stable on storage, it must issue a flush or write the
338 the data_vio if it is a write and the data is not all zeroes. The data
347 of the bio. It is vital to prevent simultaneous modifications of the
354 already operating on that logical address, it waits until the previous
355 operation finishes. It also sends a message to inform the current
356 lock holder that it is waiting. Most notably, a new data_vio waiting
358 compression packer (step 8d) rather than allowing it to continue
369 missing, it is allocated at this time out of the same physical storage
372 a. If any page-node in the tree has not yet been allocated, it must be
392 allocated, so the data_vio just traverses the tree until it finds
404 The data_vio will search each slab in a zone until it finds a free
406 it will proceed to search the next physical zone by taking the implicit
407 lock for that zone and releasing the previous one until it finds a
415 data_vio from considering it free. The reference counters are a
419 5. If an allocation was obtained, the data_vio has all the resources it
440 data_vio obtains a hash lock from the pool, adds it to the hashtable,
460 manage their own locking. The data_vio waits until it either gets a
465 order to read the data and verify that it is the same as the
466 data_vio's data, and that it can accept more references. If the
468 that address may soon be overwritten so it is not safe to use the
472 agent and any other data_vios waiting on it will record this
480 it has an allocated physical block (from step 3) that it can write
492 it will be placed in a bin (struct packer_bin) along with other
505 the packer if it cannot be paired with any other compressed block
510 are used or because it has no remaining space, it is written out
517 modified to be a shared lock. Then it releases the implicit physical
521 step 3. It will write its data to that allocated physical block.
524 lock, it will reacquire the implicit hash zone lock and share its
538 into it, possibly evicting an older cached page. The data_vio then
540 physical mapping"), if any, and records it. This step requires a lock
568 13. If the data_vio has a hash lock, it acquires the implicit hash zone
572 the struct pbn_lock it holds for its allocated block. If it had an
573 allocation that it did not use, it also sets the reference count for
574 that block back to zero to free it for use by subsequent data_vios.
579 The application bio is then acknowledged if it has not previously been
584 An application read bio follows a much simpler set of steps. It does steps
588 data from the write data_vio and return it. Otherwise, it will look up the
595 acknowledgment as in step 13, although it only needs to release the logical
600 All storage within vdo is managed as 4KB blocks, but it can accept writes
610 When a vdo is restarted after a crash, it will attempt to recover from the
616 Once each zone has some free space (or has determined that it has none),
622 If a vdo encounters an unrecoverable error, it will enter read-only mode.
624 lost. The vdo may be instructed to rebuild as best it can in order to
631 some data, it ensures that the block map and reference counts are