Performance Management



Select the Performance tab to display a configuration screen that features vari ous tuning parameters for the behavior of the system. Within this screen are the following parameters:




Request Mount Time - the maximum number of seconds that a request for a file on an off-line volume will wait for the vol ume to be mounted. If the volume is not mounted within the specified time, the user request fails.


A message is sent to the operator console requesting that the specific media be mounted. It will repeat the request and continue to wait until the operator mounts the media and the request can be processed, or until the specified time has elapsed.


      Minimum & Default = 0 seconds

      Maximum = 65535 seconds (infinite wait, no time-out)


Request Wait Time - the amount of time in seconds that a user request to read from or write to a volume waits for a drive to become available. If the request has not started within the request wait time limit, a failure message will appear, and the system will prompt for a response. It is recommended that you use the default for this value.


      Minimum = 30 seconds

      Maximum = 65535 seconds (infinite wait, no time-out)

      Default = 300 seconds


Priority Wait Time - the amount of time in seconds before a pending request for an storage drive moves into the high priority queue. This parameter allows the priority of a request to be increased the longer it waits.


The purpose is to help ensure that all requests are serviced by preventing high access volumes from hogging the drive resources. Eventually the priority should be bumped to the point where it will get serviced before the maximum wait time has expired. It is recommended that you use the default for this value.


      Minimum = 15 seconds

      Maximum = 65535 seconds (infinite wait, no time-out)

      Default = 30 seconds


Lock Time - the amount of time in seconds that a drive can be "locked" by a specific volume before requests with higher priority for different volumes may force access to the drive.

A volume will not be forced out until all current active requests for that drive are satisfied. It is recommended that you use the default for this value. The intent of Lock Time is to reduce excessive disk swapping and improve system throughput.


      Minimum = 15 seconds

      Maximum = 65535 seconds (infinite wait, no time-out)

      Default = 60 seconds


Hold Time - the minimum amount of time in seconds that a disk will remain in a drive after the last read or write request was received for that specific disk.

Note: The intent of Hold Time is to reduce excessive disk swapping and improve system throughput.


      Minimum = 1 second

      Maximum = 30 seconds

      Default = 2 seconds


Maximum SCSI Transfer Size - This setting allows the operator to change the size of the InveStore HCM buffer allocation, and to set how large the physical writes to storage are.


This value may be tuned to match the average or maximum size of the files being written.

Doing so, significantly improves performance files larger than 64Kb. Files larger than 64 Kb will see an enormous benefit from larger values.


      Minimum = 64 Kb

      Maximum = 992 Kb

      Default = 512 Kb


Per File Write Cache - This setting allows writes to be joined together before being sent to the InveStore HCM for the actual write operation to storage media. The data is NOT sent to the HCM until the set buffer is full or the file is closed by the originating application.


This setting reduces the number of buffers needed, and reduces the number of small writes sent to the storage device thereby significantly increasing the overall performance of the storage system.


This will also decrease file fragmentation for multi-thread writes to a single volume set, since it allows the cache area to filled before sending it to the HCM for the completed write operation.

For the same reason, performance is significantly improved and fragmentation is significantly decreased for files written over the network.


To improve performance, this may be set to the average file size or the maximum file size you are writing with the greatest performance improvement seen in file sizes of 64 Kb and higher.


This value is incremented in 64Kb chunks.


      Minimum = 0

      Maximum = 4 Mb

      Default = 64 Kb

Note: The greatest benefit will be realized when using server systems with higher processor speeds, along with installing the maximum amount of RAM for your server.


System Bias - determines which type of I/O operation the whole server system favors as default: Read, Write, Read-only, Write-only or None. This feature allows you to set drive bias or preference according to how your application is structured.


For example, if writes are a low priority for your application, then setting a read bias will improve read performance at the expense of writes. The correct setting will vary based on your application.


None - no bias


Read - favors read over write requests


Write - favors write over read requests


Read Only - only services read requests


Write Only - only services write requests


Enable Write Caching for UDO Drives - This setting is used to turn write caching on or off for UDO drives ONLY (Caching is automatically enabled for all other devices). Performance is significantly enhanced with write caching turned on. Caching is turned ON by default during the installation.


To turn this feature off, un-check the box to the right of the setting and select Apply and Ok.


Note: Should the system begin to experience write failures with UDO devices, turn the caching off. Performance will be significantly decreased with caching off.