Administrator Guide

Live Volume with Linux/UNIX
95 Dell EMC SC Series: Synchronous Replication and Live Volume | CML1064
|- 1:0:12:1 sdm 8:192 active ready running
|- 0:0:5:1 sdn 8:208 active ready running
|- 0:0:8:1 sdp 8:240 active ready running
|- 1:0:4:1 sdt 65:48 active ready running
`- 1:0:8:1 sdv 65:80 active ready running
vol_00 (36000d31000fba6000000000000000013) dm-3 COMPELNT,Compellent Vol
size=10G features='1 queue_if_no_path' hwhandler='0' wp=rw
`-+- policy='round-robin 0' prio=1 status=active
|- 1:0:0:1 sdc 8:32 active ready running
|- 0:0:0:1 sdb 8:16 active ready running
|- 0:0:2:1 sdf 8:80 active ready running
|- 1:0:2:1 sdg 8:96 active ready running
|- 0:0:11:1 sdr 65:16 active ready running
|- 0:0:13:1 sds 65:32 active ready running
|- 1:0:11:1 sdx 65:112 active ready running
`- 1:0:13:1 sdy 65:128 active ready running
It should be noted that even though these additional paths are shown as active and will be actively used for
I/O requests (Round Robin), any I/O requests sent to these paths will be proxied through the replication link to
the primary array for commits. The use of these paths would thus introduce unintended latency to any
applications that may be latency-adverse; at this time, path priority definitions and grouping (for example, all
paths are prio=1 by default and used in equal fashion) are not configurable between Linux hosts and SC
Series arrays. Therefore, it is not recommended to use this approach for any critical production use cases.
That being said, this scenario can still apply in certain use cases. In situations where a maintenance event
requires SC Series arrays to be powered down, the volumes on the primary array can be Live Volume
replicated to an alternate array in a different building or lab. The roles of the arrays can then be swapped,
making the alternate array adopt the primary array role (and the paths from them). The latent paths (from the
formerly primary array) can then be removed from multipath for the duration of these maintenance events
while maintaining uptime and zero disruption to any and all functions and applications that may reside on the
Linux hosts. Upon completion of these maintenance events, the volumes and roles of the arrays can then be
swapped back or left in place to the discretion of the business requirements.