• It all depends on the startegy that is being follow by your SAN team.

    If they are using thin or thick provisioning.

    With thin provisioning the disk is allocated as 100Gb but in reality it is only 10Gb on disk when the threshold is reached that disk will either alert the SAN admin or will auto grow.

    The problem that arises is the sectors that it will grow are not contigous.

    This will affect the performance of the drives as the drive head will need to skip to a new location reducing the effectiveness of read/write operations.

    I would do an IOmeter test on the server and ask SAN management to investigate.

    How fragementation affects IO response see below

    http://www.storagereview.com/toshiba_mk01grrbr_25_15k_sas_enterprise_hard_drive_review