Registry Entries - SIOS

Specifies the base TCP port number for target volume connections. This number may need to be adjusted if the default port is used by another service or is blocked by a firewall. The actual port that the target listens on is calculated as follows:

Port = TargetPortBase + (Volume Letter - A:)

For example:

TargetPortBase = 10000

Volume Letter = HPort = 10000 + (H: -A:) = 10007

Locations:

On Target System:HKEY_LOCAL_MACHINE\SYSTEM\<CurrentControlSet>\Services\ExtMirr\Parameters\TargetDispatchPort

On Source System Creating Mirror to Above Target: HKEY_LOCAL_MACHINE\SYSTEM\<CurrentControlSet>\Services\ExtMirr\Parameters\TargetDispatchPort

AND

HKEY_LOCAL_MACHINE\SYSTEM\<CurrentControlSet>\Services\ExtMirr\Parameters\Volumes\{Volume GUID}\Targets\(Target IP}\TargetDispatchPort

There are two places where this should be set if you are changing the dispatch port from 9999. On the target system, place it in the ExtMirr\Parameters key. The new setting will apply to all existing and new targets on that server. A target reboot is required when the target Parameters key has been changed for this setting to take effect. On any source system that will be creating the mirror to this target, place it in the ExtMirr\Parameters key and also in the ExtMirr\Parameters\Targets\{TargetIP} key if the mirror already exists. Note: Make sure the ports are the SAME on both the source and the target.

A firewall port must also be opened manually on all source and target servers for the new dispatch port to work.

Note: Do not change this value while the mirror is actively being resynced; you must pause the mirror prior to changing this value.

Locations:

For New Mirrors: HKEY_LOCAL_MACHINE\SYSTEM\<CurrentControlSet>\Services\ExtMirr\Parameters\WriteQueueHighWater

AND

For Existing Mirrors: HKEY_LOCAL_MACHINE\SYSTEM\<CurrentControlSet>\Services\ExtMirr\Parameters\Volumes\{Volume GUID}\Targets\{Target IP}\WriteQueueHighWater

Specifies the high water mark of the asynchronous write queue. During intensive I/O traffic, if the queue length reaches this value, the SteelEye DataKeeper driver momentarily pauses the mirror, drains the queue and automatically starts a partial resync. This value represents the number of write requests in the queue, not the number of bytes. After updating this registry value, execute the READREGISTRY command so that DataKeeper immediately starts using the new value.

Note: Do not change this value while the mirror is actively being resynced; you must pause the mirror prior to changing this value. Do not set this value higher than WriteQueueHighWater.

Locations:

For New Mirrors: HKEY_LOCAL_MACHINE\SYSTEM\<CurrentControlSet>\Services\ExtMirr\Parameters\WriteQueueLowWater

AND

For Existing Mirrors: HKEY_LOCAL_MACHINE\SYSTEM\<CurrentControlSet>\Services\ExtMirr\Parameters\Volumes\{Volume GUID}\Targets\{Target IP}\WriteQueueLowWater

This value is used to specify the maximum number of resync block requests that can be queued up at the same time. Changing this value may change the speed of mirror resynchronizations - a higher value often leads to a faster resync at the cost of increased memory usage during resync. The value specified in WriteQueueLowWater is half the number of resync block requests. After updating this registry value, execute the READREGISTRY command so that DataKeeper immediately starts using the new value.

DataKeeper target snapshot uses a default block size of 64KB for all entries that are written to the snapshot file. This block size can be modified by creating this TargetSnapshotBlocksize registry key.

The value should always be set to a multiple of the disk sector size, which is usually 512 bytes. Certain workloads and write patterns can benefit from changing the block size. For example, a volume that is written in a sequential stream of data (e.g. SQL Server log files) can benefit from a larger block size. A large block size results in fewer reads from the target volume when consecutive blocks are written. But a volume that is written in a random pattern may benefit from a smaller value or the default 64KB. A smaller block size will result in less snapshot file usage for random write requests.