Technical White Paper Dell EMC Unity: High Availability A Detailed Review Abstract This white paper discusses the high availability features on Dell EMC Unity™ purpose-built solution. June 2021 H15162.4 Revisions Revisions Date Description May 2016 Initial release – Unity OE 4.0 June 2021 Template and format updates. Updated for Unity OE 5.1 Acknowledgments Author: Ryan Poulin The information in this publication is provided “as is.” Dell Inc. makes no representations or warranties of any kind with respect to the information in this publication, and specifically disclaims implied warranties of merchantability or fitness for a particular purpose. Use, copying, and distribution of any software described in this publication requires an applicable software license. This document may contain certain words that are not consistent with Dell's current language guidelines. Dell plans to update the document over subsequent future releases to revise these words accordingly. 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[6/18/2021] [Technical White Paper] [H15162.4] 2 Dell EMC Unity: High Availability | H15162.4 Table of contents Table of contents Revisions............................................................................................................................................................................. 2 Acknowledgments ............................................................................................................................................................... 2 Table of contents ................................................................................................................................................................ 3 Executive summary ............................................................................................................................................................. 4 Audience ............................................................................................................................................................................. 4 1 Introduction ................................................................................................................................................................... 5 1.1 Terminology ........................................................................................................................................................ 5 2 Storage Processors ...................................................................................................................................................... 7 2.1 Management software ........................................................................................................................................ 9 2.2 Storage processor memory .............................................................................................................................. 10 2.3 Battery Backup Units ........................................................................................................................................ 11 2.4 Power supplies ................................................................................................................................................. 12 2.5 Cooling modules ............................................................................................................................................... 12 2.6 Backend bus connectivity ................................................................................................................................. 12 3 RAID configuration ..................................................................................................................................................... 15 3.1 RAID 1/0 ........................................................................................................................................................... 15 3.2 RAID 5 .............................................................................................................................................................. 15 3.3 RAID 6 .............................................................................................................................................................. 16 3.4 Hot spares ........................................................................................................................................................ 16 4 Block storage .............................................................................................................................................................. 18 4.1 iSCSI configuration ........................................................................................................................................... 19 4.2 Fibre Channel configuration ............................................................................................................................. 20 4.3 Block example .................................................................................................................................................. 21 5 File storage ................................................................................................................................................................. 23 5.1 Failback policy .................................................................................................................................................. 23 5.2 Link Aggregation Control Protocol (LACP) ....................................................................................................... 24 5.3 Fail Safe Networking (FSN) .............................................................................................................................. 25 5.4 SMB 3.0 Continuous Availability....................................................................................................................... 26 5.5 File example ..................................................................................................................................................... 26 6 Replication .................................................................................................................................................................. 28 7 Conclusion .................................................................................................................................................................. 29 A Technical support and resources ............................................................................................................................... 30 A.1 Related resources............................................................................................................................................. 30 3 Dell EMC Unity: High Availability | H15162.4 Executive summary Executive summary Having constant access to data is a critical component in any modern business. If data becomes inaccessible, business operations may be impacted and potentially cause revenue to be lost. Because of this, IT administrators are tasked with ensuring every component in the data center does not have a single point of failure. This white paper discusses the high availability features that are available on the purpose-built Dell EMC Unity™ system to ensure data access is continuously available. Audience This white paper is intended for Dell EMC customers, partners, employees, and any others involved in evaluating, acquiring, managing, operating, or designing a highly available environment using Dell EMC Unity. 4 Dell EMC Unity: High Availability | H15162.4 Technical support and resources 1 Introduction The Dell EMC Unity™ purpose-built solution features fully redundant hardware and includes several high availability features. These are designed to withstand component failures within the system itself as well as in the environment, such as network or power. If an individual component fails, the storage system can remain online and continue to serve data. The system can also withstand multiple failures if they occur in separate component sets. After the administrator is alerted about the failure, they can easily order and replace the failed component without any impact. This white paper discusses the redundant hardware and high availability features that are available on Dell EMC Unity and Dell EMC Unity XT, which enables the systems to obtain 99.999% availability. 1.1 Terminology Asymmetric Logical Unit Access (ALUA): A SCSI standard for multi-pathing that advertises one path as active/optimized and the other as active/non-optimized. Battery Backup Unit (BBU): A lithium-ion battery located within each Storage Processor that is used to power the system when power is lost. It keeps the SP online while it flushes the cached content to the M.2 device. Common Messaging Interface (CMI): A high speed bus that is used for communication between SPs, such as mirroring write cache or redirecting I/Os from a non-optimized path. Disk Array Enclosure (DAE): Hardware that includes either 15 x 3.5”, 25 x 2.5”, or 80 x 2.5” drive