Emc IP Holding Company LLC

Dell Products Inc.

Jiahui Wang

Peng Yin

Rong Yu

Lixin Pang

Peng Wu

Kuolin Hua

Stephen Richard Ives

Kunxiu Gao

Ningdong Li

Daohong Wang

Michael J Scharland

Ofer Michael

Qun Fan

Seema G Pai

Mohammed Asher

Hagay Dagan

Michael Garvey

Shao Hu

Christopher Monti

Li Lang

Timothy Johnson

Sean Hu

Akash Agrawal

In a drive cluster in which multiple parity EC (N+P) is implemented, rebuild-related reads are balanced across drives for recovery from drive failure. N members per protection group are read and (P−1) members are skipped, where skipping a member means omission from member rebuild calculations. Per-disk skip counts are calculated, and members that are eligible to be skipped are selected such that per-disk read counts are balanced.

Load balancing for erasure coding with multiple parities

A method comprising: detecting a storage device failure in a storage array, the storage array including a plurality of storage devices, the storage device failure being a failure of one or more of the plurality of storage devices; wherein: the plurality of storage devices are configured to implement a supergroup including a plurality of subgroups; identifying ones of the plurality of subgroups that are affected by the storage device failure; and rebuilding the identified subgroups, wherein: (A) when a count of failed storage device is less than a first threshold, each of the identified subgroups is rebuilt based only on subgroup parity components for the subgroup without the use of supergroup parity components, and (B) when the count of failed storage devices is between the first threshold and the second threshold, each of the identified subgroups is rebuilt based on both subgroup and supergroup parity components.

Hierarchical parity protection groups for efficient data recovery

One or more aspects of the present disclosure relate to performant destaging of write pending (WP) data to disk. In embodiments, an input/output (IO) workload is received at a storage array. Additionally, the IO workload can include an IO request with a random write request. Further, a write destage context for write-pending (WP) data corresponding to the random write request can be generated by a data services engine of the storage array. In addition, using the write destage context, a disk adapter (DA), at a backend of the storage array, is enabled to destage write-pending (WP) data without reading from a target write location of the random write request on a storage device on the storage array.

Performant write pending data destaging

A data service layer running on a storage director node generates a request to destage host data from a plurality of cache slots in a single back-end track. The destage request includes pointers to addresses of the cache slots and indicates an order in which the host application data in the cache slots is to be included in the back-end track. A back-end redundant array of independent drives (RAID) subsystem running on a drive adapter is responsive to the request to calculate parity information using the host application data in the cache slots. The back-end RAID subsystem assembles the single back-end track comprising the host application data from the plurality of cache slots of the request, and destages the single back-end track to a non-volatile drive in a single back-end input-output (IO) operation.

Destaging multiple cache slots in a single back-end track in a RAID subsystem

Distributed failover of a failed BE, and failback of the failed BE when it recovers, are described. A separate pool of memory may be reserved for each BE on a storage system. Each such pool may be further divided into sub-pools. When a BE fails, the one or more other active BEs on the storage system may be notified, and each such active BE may attempt to take ownership of one or more sub-pools of the BE and execute the one or more pending write operations of the failed BE. Upon completing execution of the pending write operations in a failed-over sub-pool, the ownership of the sub-pool may be returned to the failed BE. When the failed BE recovers, the recovered BE may attempt to take back control of one or more of its sub-pools.

Distributed failover of a back-end storage director

A storage system that supports multiple RAID levels presents storage objects with front-end tracks corresponding to back-end tracks on non-volatile drives and accesses the drives using a single type of back-end allocation unit that is larger than a back-end track. When the number of members of a protection group of a RAID level does not align with the back-end allocation unit, multiple back-end tracks are grouped and accessed using a single IO. The number of back-end tracks in a group is selected to align with the back-end allocation unit size. If the front-end tracks are variable size, then front-end tracks may be destaged into a smaller number of grouped back-end tracks in a single IO.

Group-based RAID-1 implementation in multi-RAID configured storage array

A storage array that presents a logical storage device to hosts that is accessed using front-end tracks and access tangible managed drive using back-end tracks locates multiple front-end tracks in individual back-end tracks. Error-correcting codes are used to identify different front-end tracks in a back-end track when the back-end track is copied from the managed drives into storage array memory. CKD front-end tracks can be split into multiple partial CKD front-end tracks that are located at contiguous address space in different back-end tracks. The front-end tracks that are located in a particular back-end track may be selected to reduce or minimize unused space. The front-end tracks in a back-end track may be logically stored on different production volumes.

Multi-BCRC raid protection for CKD

Techniques for performing configuration may include: determining an initial distribution of logical devices among disk adapters, wherein the initial distribution assigns each logical device a designated disk adapter as a primary active disk adapter servicing I/Os directed to the logical device, wherein the logical devices have storage provisioned from a RAID group including physical storage devices, wherein the disk adapters concurrently issue I/Os to each of the physical storage devices; detecting a configuration change; and responsive to detecting a configuration change, performing first processing. The first processing may include determining, in accordance with the configuration change, a redistribution of the logical devices among the disk adapters; and draining pending I/Os. The configuration change may include adding or removing a logical device provisioned from the RAID group. Performing a first operation on a storage device of the RAID group may include synchronous draining of I/Os of the storage device.

Techniques for multiple directors concurrently servicing I/Os directed to same physical storage devices

A SAN storage node has multiple engines, each including at least one computing node with at least one drive adapter for accessing arrays of drives. All drives of the SAN node are accessible by all drive adapters. The drives are organized into hypers. Each hyper is accessible to all drive adapters. Each drive is temporarily associated with a preferred owner for spin-up. A drive adapter that initializes spin-down of one of the drives takes a spindle lock on the drive being spun-down and prompts all other drive adapters to complete outstanding IOs on the drive being spun-down.

Storage array with N-way active-active backend

A method of distributed management of recovery of multi-controller NVMe drives includes detecting a path failure of a PCIe path from a first storage node to a first controller on the multi-controller NVMe drive, and initially attempting to correct the path failure using a controller level reset. If the controller level reset is unsuccessful, an alternative path to the controller is sought, and if that is unsuccessful a drive level reset operation is coordinated by all storage nodes with controllers executing on the NVMe drive. To coordinate reset of the NVMe drive, one storage node is elected master. Each node (both slave and master) initiates quiescing of IO operations on its respective controller, and after quiescing has completed, initiates shutdown of its respective controller. Once all controllers are shut down, the master initiates reset of the NVMe drive. Timeouts are used to constrain completion of the quiescing and shutdown operations.

System and method for managing recovery of multi-controller NVMe drives

Described are techniques for processing a data request for a device of a data storage system. A data request directed to a device that is a virtualized device of the data storage system is received. The data storage system has a plurality of devices comprising one or more local devices and one or more virtualized devices. Each of the local devices is a storage device included in the data storage system and each of the virtualized devices is an external storage device with respect to the data storage system and is presented as a local storage device of the data storage system. First processing is performed by a disk adapter in connection with servicing the data request for the device. The first processing includes sending the request to an external storage device corresponding to the virtualized device over a connection in accordance with path information obtained from discovery processing.

Growing community of inventors

Framingham, MA, United States of America

Jiahui Wang