Unmount file system unmount or unassign drive letter

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Unmount file system (unmount or unassign drive letter to flush the filesystem buffers from the host memory down to the VMAX3 array) Deactivate the Volume Group A failover leads to a write disabled state of the R1 devices. If a device suddenly becomes write disabled from a read/write state, the reaction of the host can be unpredictable if the device is in use. Hence the recommendation to stop applications, unmount filesystem/unassign drive letter, prior to performing a failover for maintenance operations. SRDF/Synchronous Operations
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24 Copyright 2015 EMC Corporation. All rights reserved. As seen in the output, the R1s are now Write Disabled, the links are set to Not Ready and the R2s are Read Write enabled. As application processing has been started using the R2 devices, we see that there are invalid tracks accumulating (R1 Inv Tracks) on the target Array. These are the changes that are being made to the R2 devices. When it is time to return to the source Array, these invalid tracks will be incrementally synchronized back to the source. The pair state is reflected as Failed Over. Note that we have created a device group named synctgtdg on the remote host that is accessing the R2 devices. So we have created a device group of type RDF2 and have added the R2 devices to it. The query was executed on the remote host and shows the state from the perspective of the R2 devices. SRDF/Synchronous Operations
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25 Copyright 2015 EMC Corporation. All rights reserved. While the target (R2) device is still operational (Read Write Enabled to its local host), an incremental data copy from the target (R2) device to the source (R1) device can be initiated in order to update the R1 mirror with changed tracks from the target (R2) device. After an extended outage on the R1 side, a substantial amount of invalid tracks could have accumulated on the R2. If a failback is now performed, production starts from the R1. New writes to the R1 have to be transferred to the R2 synchronously. Any track requested on the R1 that has not yet been transferred from the R2 has to be read from across the links. This could lead to performance degradation on the R1 devices. The update operation helps to minimize this impact. When performing an update, the R1 devices are still “Write Disabled”; the links become “Read Write” enabled because of the “Updated” state. The target devices (R2) remain “Read Write” during the update process. The update operation can be used with the until flag, which represents a skew value assigned to the update process. For example, you can choose to update until the accumulated invalid tracks is down to 30000. Then a failback operation can be executed. SRDF/Synchronous Operations
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26 Copyright 2015 EMC Corporation. All rights reserved. When the update operation is performed after a failover, the links become Read/Write enabled, but the Source devices are still Write disabled. Production work continues on the R2 devices.
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