Dell EMC Metro node 7.1 Administrator Guide

About transfer-size

Transfer-size can be as small 40 K, as large as 128 M, and must be a multiple of 4 K. The default recommended value is 128 K.

A larger transfer-size results in higher performance for the migration, but may negatively impact front-end I/O. This is especially true for metro node Metro migrations.

A smaller transfer-size results in lower performance for the migration, but creates less impact on front-end I/O and response times for hosts.

Set a large transfer-size for migrations when the priority is data protection or migration performance. Set a smaller transfer-size for migrations when the priority is front-end storage response time.

Factors to consider when specifying the transfer-size:

• For metro node Metro configurations with narrow inter-cluster bandwidth, set the transfer size lower so the migration does not impact inter-cluster I/O.
• The region specified by transfer-size is locked during migration. Host I/O to or from that region is held. Set a smaller transfer-size during periods of high host I/O.
• When a region of data is transferred, a broadcast is sent to the system. Smaller transfer-size mean more broadcasts, slowing the migration.

Use the batch-migrate start command to start the specified batch migration:

For example:

VPlexcli:/> batch-migrate start --file migrate.txt --transfer-size 2M
Started 4 of 4 migrations.