EMC has traditionally protected failing drives using Dynamic Spares. A Dynamic Spare will take a copy of the data from a failing drive and act as a temporary mirror of the data until the drive can be replaced. The data will then be copied back to the new drive at which point the Dynamic Spare will return the spare drive pool. Two copy processes are required one to copy data to the Dynamic Spare and one to copy data back to the new drive. The copy process may impact performance and, since the Dynamic Spare takes a mirror position, can affect other dynamic devices such as BCVs.


Permanent Sparing overcomes many of these limitations by copying the data only once to a drive which has replaced the failing drive taking its original mirror position. Since the Permanent Spare

does not take an additional mirror position it will not affect Timfinder Mirror operations.

Permanent Sparing in some instances uses Dynamic Sparing as an interim step. This will be described together with the requirements for Permanent Sparing.


- Permanent Sparing is supported on all flavours of DMX.

- A Permanent Spare replaces the original failing drive and will take its original mirror position.

- Required sufficient drives of the same type as the failing drives to be installed and configured as Spares.

- Needs to enabled in the binfile (can be done via Symcli).

- Permanent Sparing will alter the back end bin and cannot be initiated when there is a Configuration Lock on the box.

- When enabled reduces the need for a CE to attend site for drive changes since drives can be replaced in batches.

- Permanent Spare will follow all configuration rules to ensure both performance and redundancy.

- Enginuity Code level must support the feature.


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I am EMC Technology Architect. I design EMC SAN Solution and have expertise in EMC SAN product. More info:- diwakar@emcstorageinfo.com
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