Emc IP Holding Company LLC

Dell Products Inc.

Evgeny Malkevich

Edward S Robins

Kuolin Hua

Stephen Richard Ives

Kunxiu Gao

Seema G Pai

Kevin Granlund

Roii Raz

Barak Bejerano

In a storage system that implements RAID (D+P) protection groups a drive subset initially has (D+P) drives plus a spare drive with (D+P) splits. Spare splits are distributed with drive index and split index adjacency such that no single drive or split index contains multiple spare splits. When the drive subset is incremented by one drive a group of selected splits are relocated to the new drive based on drive index and split index adjacency such that no single drive or split index contains multiple members of a new protection group. If one of the drives is failing or fails, then an adjusted spare split index value is calculated for each protection group member on that drive so that the protection group members are rebuilt or relocated without placing more than one member of any protection group on a single drive. Adjusted spare split index values may be calculated in steps using the data split indices in ascending order and the largest drive indices in descending order.

Flexible raid sparing using disk splits

Each drive in a cluster is organized into splits of a single size. The splits are used as protection group members for a selected RAID level. Individual clusters can be scaled up with a number of new drives that is less than the number of protection group members for the RAID level by redistributing some data/parity to splits of the new drives. Splits are selected for redistribution such that new protection groups are created. If the number of new drives is equal to or greater than the number of protection group members for the RAID level, then new clusters may be created using the new drives. Any remaining drives are used to scale-up individual clusters.

Scaling raid-based storage by redistributing splits

A distributed network of storage elements (DNSE) is provided in which the physical capacity of each drive is split into a set of equal sized logical splits which are individually protected within the DNSE using separate RAID groups. To reduce restoration latency, members of the RAID groups having a member in common on a given drive are spread within the DNSE to minimize the number of sets of drives within the DNSE that have RAID members in common. By causing the splits to be protected by RAID groups, restoration of the splits may occur in parallel involving multiple drives within the DNSE. By minimizing the overlap between RAID members on various drives, failure of a given drive will not require multiple reads from another drive in the DNSE. Likewise, spare splits are distributed to enable write recovery to be performed in parallel on multiple drives within the DNSE.

Allocating RAID storage volumes across a distributed network of storage elements

Configuring spare sections in a system having a plurality of devices and having a plurality of erasure encoding groups, each of the devices having a plurality of sections and each of the groups having a plurality of members located on the sections of the devices, includes configuring the system to have a plurality of erasure encoding groups with no spare sections, ordering the groups according to desirability of converting members of each of the groups into spare sections, converting members of a subset of the groups into spare sections according to ordering of the groups, and determining if the spare sections for the system provide sufficient coverage for the system in response to failure of each of the devices. The erasure encoding may be a RAID encoding.

Optimizing spare capacity and spare distribution

Embodiments are directed to techniques for techniques for selecting a proper set of spare sections to use in a given failure scenario. These embodiments use a set of rules to define which spare sections are eligible to serve as spares for reconstruction of the RAID members on a disk that had failed. In addition, the set of rules may include weighted rules to allow optimization in the spare selection process.

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Newton, MA, United States of America

Evgeny Malkevich