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Dell EMC Solutions Enabler 9.2 SRDF Family CLI User Guide

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Update R1 mirror

The update operation starts an update of the source (R1) side after a failover while the target (R2) side may still be operational to its local hosts.

Use update to perform an incremental data copy of only the changed tracks from the target (R2) device to the source (R1) device while the target (R2) device is still Write Enabled to its local host.

SRDF updates each specified SRDF pair in a device group as follows:

  1. Suspend the SRDF (R1 to R2) links when the SRDF links are up.
  2. If there are invalid remote (R2) tracks on the source side and the force option was specified, mark tracks that were changed on the source devices for refresh from the target side.
  3. Refresh the invalid tracks on the source (R1) side from the target R2 side. The track tables are merged between the R1 and R2 sides.
  4. Resume traffic on the SRDF links.
NOTE:

If you update R1 while the SRDF pair is Suspended and not ready at the source, the SRDF pair types are in an Invalid state when the update completes. To resolve this condition, use the rw_enable r1 operation to make the SRDF pairs become Synchronized.

When the update is complete, the pairs are in the R1 Updated state.

The following image shows an update of an SRDF pair.

Figure 1. Update SRDF device track tables
NOTE:

When you issue the symrdf command, device external locks are set on all SRDF devices you are about to control. See Device external locks and Table 1.

Syntax

Use update for a device group, composite group, storage group, or device file: 

symrdf -g DgName update
symrdf -cg CgName update
symrdf -sg SgName update
symrdf -f[ile] FileName update

Use the update -until # command for scenarios where you want I/O to continue from the remote host and periodically update an inactive R1 device over an extended period of time.

Options

-until
Checks the number of invalid tracks that are allowed to build up from the active R2 local I/O before another update (R2 to R1 copy) is triggered. The update sequence loops until the invalid track count is less than the number specified by the # value
If the invalid track count is less than the number of tracks specified by the -until # value, the command exits. Otherwise, the following sequence of operations for update R1 mirror is retriggered until the threshold is reached.
  1. Update the R1 mirror.
  2. Build changed tracks on R2.
  3. Check the invalid track count.

Examples

To update all the source (R1) devices in the SRDF pairs, for device group prod:

symrdf -g prod update

To update the R1 mirror of device group prod continuously until track the number of tracks to be copied is below 1000:

symrdf -g prod update -until 1000

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