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RAIDWatch User’s Manual

function to decide at what interval the subsystem will check the status

of these devices.

 Drive Fail Swap Check Period (Sec): The subsystem scans drive

buses at this interval to check if a failed drive has been replaced.

 Maximum Tag Count: The subsystem supports tag command

queuing with an adjustable maximum tag count from 1 to 128. The

default setting is “Enabled” with a maximum tag count of 32.

Host-side Parameters

 Maximum Queued I/O Count: This is the arrangement of the

controller internal resources for use with a number of the current host

nexus. It is a "concurrent" nexus, so when the cache is cleared up, it

will accept a different nexus again. Many I/Os can be accessed via

the same nexus.

This function allows you to configure the maximum number of I/O

queues the controller can accept from the host computer.

 LUNs per Host ID: Each SCSI ID can have up to 32 LUNs (Logical

Unit Numbers). A logical configuration of array capacity can be

presented through one of the LUNs under each host channel ID. Most

SCSI host adapters treat a LUN like another SCSI device.

 Max. Concurrent Host-LUN: The configuration option adjusts the

internal resources for use with a number of current host nexus. If

there are four host computers (A, B, C, and D) accessing the array

through four host IDs/LUNs (ID 0, 1, 2 and 3), host A through ID 0

(one nexus), host B through ID 1 (one nexus), host C through ID 2

(one nexus) and host D through ID 3 (one nexus) - all queued in the

cache - that is called 4 nexus. If there are I/Os in the cache through

four different nexus, and another host I/O comes down with a nexus

different than the four in the cache (for example, host A access ID 3),

the controller will return "busy.” Note that it is "concurrent" nexus; if

the cache is cleared up, it will accept four different nexus again.

Many I/Os can be accessed via the same nexus.

 Tag Reserved Per Host-LUN Connection: Each nexus has 32 (the

default setting) tags reserved. When the host computer sends 8 I/O

tags to the controller, and the controller is too busy to process them

all, the host might start to send less than 8 tags during every certain

period of time since then. This setting ensures that the controller will

accept at least 32 tags per nexus. The controller will be able to accept

more than that as long as the controller internal resources allow - if

the controller does not have enough resources, at least 32 tags can be

accepted per nexus.

7-16 Host-side, Drive-side, and Disk Array Parameters

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Vicon IX 2000 L Manual de usuario Pagina 146