Dell Products Inc.

Elad Grupi

Eldad Zinger

Vitaly Zharkov

Amit Engel

Access control data stored in the storage servers of a distributed data storage system is modified according to received access control commands and accessed to process host I/O requests without requiring the use of locks. Processing of certain access control commands includes allocating a new volume descriptor to store the updated access control data for a corresponding storage volume, and remapping the storage volume to the new volume descriptor with a single write operation. Each volume descriptor stores both reservation type and reservation holder data for the corresponding storage volume within a single memory register, allowing host I/O request processing logic to read both reservation type and reservation holder using a single read operation, and access control command processing logic to modify both reservation type and reservation holder using a single write operation. A registrants bitmap in the volume descriptor represents hosts registered for the corresponding storage volume.

Access control command processing in a distributed data storage system

Deferred memory page allocation commands and non-deferred memory page allocation commands are identified within host I/O commands received by a data storage system. For each one of those received host I/O commands that are identified as a deferred memory page allocation command, QoS (Quality of Service) policy enforcement is performed before any memory pages are allocated by the data storage system to store host data indicated by the received command. Host I/O commands that are identified as deferred memory page allocation commands include read commands, and host I/O commands that are identified as non-deferred memory page allocation commands include in-capsule write commands. For commands identified as deferred memory page allocation commands, enforcing QoS policy before any memory pages are allocated to store host data indicated by the command avoids the possibility of enqueueing the allocated memory pages onto the QoS wait queue, thus conserving data storage system memory resources.

Quality of service (QOS) enforcement while conserving memory resources in a data storage system

Technology is disclosed for QoS (Quality of Service) enforcement with reduced contention. For commands where the QoS wait queue is empty and the QoS credit count is sufficient, an atomic operation subtracts the credits required to process the command from the QoS credit count without locking, and the command is processed. For other commands, credit generation is attempted by first reading a lock flag without obtaining a lock. If the lock flag is clear, an atomic operation sets it, and credit generation is performed if sufficient time has passed since a last credit generation. Credit generation stores a sum of the current QoS credit count and the number of newly generated credits into a local credit count, and processes commands in the QoS wait queue for which sufficient credits exist in the local credit count. When credit generation completes, the local credit count is stored into the QoS credit count.

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Pardes Hana, Israel

Elad Grupi