Abstract: An aspect of space accounting includes providing a counter for each of a plurality of key/value pairs for storage system operations. The key uniquely identifies a logical storage unit on which operations associated with the key are performed, the value identifies an amount of data usage with respect to the operations performed on the logical storage unit, and the counter tracks a type of the operations. An aspect also includes tracking, via corresponding counters, updates to a read/write (RW) tablet associated with a Cuckoo tree. The tracking includes updating a filter to include instances of key/value pairs and the RW tablet in which the pairs are stored. An aspect further includes tracking a plurality of read-only (RO) tablets associated with the Cuckoo tree. The tracking includes updating the filter to include instances of key/value pairs and one or more of the RO tablets in which the pairs are stored.

Abstract: A method, computer program product, and computer system for staging writes into a log in chronological order, wherein each write may have a log record of a plurality of log records describing data of the write. The log record may be organized into a bucket of a plurality of buckets associated with a range of a plurality of ranges within a backing store, wherein each bucket of the plurality of buckets may include two keys respectively. The log record of the plurality of log records may be flushed from the bucket of the plurality of buckets to the backing store at a location and in an order determined based upon, at least in part, the two keys included with the bucket.

Abstract: An aspect of implementing a Cuckoo tree includes providing a Cuckoo filter table for performing lookups in a Cuckoo tree. The table tracks fingerprints of keys and tablets in which the keys reside. An aspect also includes providing a stash configured to manage duplicate keys in the tree. The stash includes: a key hash table that stores full keys corresponding bucket index references that point to a reverse time ordered list of values corresponding to the full keys; and a value store having buckets with slots for storing the list. An aspect further includes setting a duplicate threshold value in the tree that provides a limit on a number of fingerprints that can exist in a bucket. During a store operation on a key, upon determining the number of existing entries with same fingerprint in target bucket would exceed the threshold, another bucket is selected for the key.

Abstract: A method, computer program product, and computer system for staging writes into a log in chronological order, wherein each write may have a log record of a plurality of log records describing data of the write. The log record may be organized into a bucket of a plurality of buckets associated with a range of a plurality of ranges within a backing store, wherein each bucket of the plurality of buckets may include two keys respectively. The log record of the plurality of log records may be flushed from the bucket of the plurality of buckets to the backing store at a location and in an order determined based upon, at least in part, the two keys included with the bucket.

Abstract: An aspect of implementing a Cuckoo tree includes providing a Cuckoo filter table for performing lookups in a Cuckoo tree. The table tracks fingerprints of keys and tablets in which the keys reside. An aspect also includes providing a stash configured to manage duplicate keys in the tree. The stash includes: a key hash table that stores full keys corresponding bucket index references that point to a reverse time ordered list of values corresponding to the full keys; and a value store having buckets with slots for storing the list. An aspect further includes setting a duplicate threshold value in the tree that provides a limit on a number of fingerprints that can exist in a bucket. During a store operation on a key, upon determining the number of existing entries with same fingerprint in target bucket would exceed the threshold, another bucket is selected for the key.

Abstract: An aspect of space accounting includes providing a counter for each of a plurality of key/value pairs for storage system operations. The key uniquely identifies a logical storage unit on which operations associated with the key are performed, the value identifies an amount of data usage with respect to the operations performed on the logical storage unit, and the counter tracks a type of the operations. An aspect also includes tracking, via corresponding counters, updates to a read/write (RW) tablet associated with a Cuckoo tree. The tracking includes updating a filter to include instances of key/value pairs and the RW tablet in which the pairs are stored. An aspect further includes tracking a plurality of read-only (RO) tablets associated with the Cuckoo tree. The tracking includes updating the filter to include instances of key/value pairs and one or more of the RO tablets in which the pairs are stored.

Abstract: A method may include generating a chain of snapshot point-in-time copies (PITCs) for a virtual volume, the chain comprising one or more reverse PITCs and one active PITC, such that: (i) read operations to a snapshot pointing to a reverse PITC traverse a portion of the one or more reverse PITCs in a direction of the chain from the reverse PITC pointed to by the snapshot to the active PITC in order to return data responsive to the read operations to the snapshot; and (ii) read operations to the virtual volume traverse only the active PITC in order to return data responsive to the read operations to the virtual volume.