Load balancing technique for a storage array

Patent metadata

Field	Value
Publication number	US-2016231948-A1
Application number	US-201514619934-A
Country	US
Kind code	A1
Filing date	Feb 11, 2015
Priority date	Feb 11, 2015
Publication date	Aug 11, 2016
Grant date	—

Abstract

A technique for load balancing uses heuristic-based algorithms with respect to input/output (I/O) latency of workloads destined to storage devices, e.g., solid state drives (SSDs), of a storage array attached to a storage system. Illustratively, “front-end” requests received from a host result in a back-end workload as those requests are processed by a storage I/O stack of the storage system and stored on the storage array. Accordingly, the technique maintains a consistent latency for the host requests (front-end) to control latency for the back-end workload. The load balancing technique illustratively load balances fixed (back-end) workloads having similar I/O sizes and I/O patterns. Illustratively, the technique balances the workloads across a plurality of storage ports over one or more I/O paths to the SSDs. Access to the SSDs may then be distributed among the storage ports.

First claim

What is claimed is:

1 . A method comprising:
receiving a plurality of write requests directed towards a logical unit (LUN), each write request having data, the write request processed at a storage system having a memory and a processor, the storage system having one or more storage controllers attached to one or more shelves of solid state drives (SSDs); generating an input/output (I/O) workload from the plurality of write requests; and controlling a back-end latency of the I/O workload to the SSDs such that the plurality of write requests maintain a predictable front-end latency.

2 . The method of claim 1 further comprising:
load balancing the I/O workload among a plurality of I/O channels included in the one or more storage controllers.

3 . The method of claim 2 , wherein each SSD is associated with a primary I/O path and a secondary I/O path to the one or more storage controllers, and wherein the load balancing of the I/O workload includes sending data across the primary I/O path and the secondary I/O path for each SSD.

4 . The method of claim 2 , further comprising:
predicting an expected load on each I/O channel of the plurality of I/O channels by looking ahead into an I/O queue having the I/O workload.

5 . The method of claim 2 , wherein each SSD is associated with a primary I/O path and a secondary I/O path to the one or more storage controllers, wherein the load balancing of the I/O workload includes sending data across the primary I/O path for each SSD, and wherein the secondary I/O path is a failover I/O path for each SSD.

6 . The method of claim 1 further comprising:
reading a temperature of each respective SSD; and
in response to the temperature of the respective SSD being outside of an operating temperature range, issuing a warmup I/O request to the respective SSD.

7 . The method of claim 2 wherein load balancing the I/O workload includes calculating a number of I/O operations per second of the workload for each port.

8 . The method of claim 2 wherein load balancing the I/O workload includes calculating a I/O latency histogram of the I/O workload for a plurality of durations.

9 . The method of claim 4 wherein the load balancing the I/O workload includes examining a reads pending count and a writes pending count indicating a respective number of read and write requests associated with the I/O queue.

10 . The method of claim 5 further comprising:
monitoring stream-open durations for a first SSD and a second SSD, wherein the first and second SSDs are multi-streaming; and
in response to the first SSD having stream-open durations greater than an average stream-open duration and the second SSD having stream-open durations less than the average stream-open duration, exchanging a first primary I/O path associated with the first SSD with a second primary I/O path associated with the second SSD.

11 . A method comprising:
receiving a plurality of write request directed towards a logical unit (LUN), each write request having data, the write request processed at a storage system having a memory and a processor, the storage system having one or more storage controllers attached to one or more shelves of multi-stream solid state drives (SSDs); generating an input/output (I/O) workload from the plurality of write requests, the workload including the data and metadata associated with the data; and controlling a back-end latency of the I/O workload to the SSDs such that the plurality of write requests maintain a predictable front-end latency, wherein a first stream for each SSD is used for the data and a second stream different from the first stream for each SSD is used for the metadata.

12 . A system comprising:
a storage system having a memory connected to a processor via a bus; one or more storage shelves coupled to the storage system via one or more storage controllers, the storage shelves having a plurality of solid state drives (SSDs); a storage I/O stack executing on the processor of the storage system, the storage I/O stack when executed operable to:
receive a plurality of write requests directed towards a logical unit (LUN), each write request having data;
generate an input/output (I/O) workload from the plurality of write requests; and
control a back-end latency of the I/O workload to the SSDs such that the plurality of write requests maintain a predictable front-end latency.

13 . The system of claim 12 wherein the storage I/O stack is further operable to:
load balancing the I/O workload among a plurality of I/O channels included in the one or more storage controllers.

14 . The system of claim 13 , wherein each SSD is associated with a primary I/O path and a secondary I/O path to the one or more storage controllers, and wherein the load balancing of the I/O workload includes sending data across the primary I/O path and the secondary I/O path for each SSD.

15 . The system of claim 13 wherein the storage I/O stack is further operable to:
predict an expected load on each I/O channel of the plurality of I/O channels by looking ahead into an I/O queue having the I/O workload.

16 . The system of claim 13 , wherein each SSD is associated with a primary I/O path and a secondary I/O path to the one or more storage controllers, and wherein the load balancing of the I/O workload includes sending data across the primary I/O path for each SSD, and wherein the secondary I/O path is a failover I/O path for each SSD.

17 . The system of claim 12 wherein the storage I/O stack is further operable to:
read a temperature of each respective SSD; and
in response to the temperature of the respective SSD being outside of an operating temperature range, issue a warmup I/O request to the respective SSD.

18 . The system of claim 13 wherein load balancing the I/O workload includes calculating a number of I/O operations per second of the workload for each port.

19 . The system of claim 13 wherein load balancing the I/O workload includes calculating a I/O latency histogram of the I/O workload for a plurality of durations.

20 . The system of claim 15 wherein the load balancing the I/O workload includes examining a reads pending counter and a writes pending counter indicating a respective number of read and write requests associated with the I/O queue.

Assignees

• Netapp Inc

Inventors

• Gupta Anish
• Mohammed Samiullah
• Nguyen Jamie
• Lu Hung

Classifications

• G06F3/067

  Distributed or networked storage systems, e.g. storage area networks [SAN], network attached storage [NAS] · CPC title

• G06F3/0611 Primary

  in relation to response time · CPC title

• G06F3/0635

  by changing the path, e.g. traffic rerouting, path reconfiguration · CPC title

• G06F3/0659

  Command handling arrangements, e.g. command buffers, queues, command scheduling · CPC title

• G06F3/0653

  Monitoring storage devices or systems · CPC title