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Chapter 2 HPSS Planning
HPSS Installation Guide September 2002 99
Release 4.5, Revision 2
In Table 2-3:
• Disk Type is the specific type of media to which the values in the row apply.
• Media Block Size is the block size to use in the storage class definition. For disk, this value
should also be used when configuring the Mover devices that correspond to this media
type. Note that this value will not limit the amount of data that can be read from or written
to a disk in one operation—it is used primarily to perform block boundary checking to
ensure that all device input/output requests are block aligned. This value should
correspond to the physical block size of the disk device.
• Minimum Access Size is the smallest size data access requests that should regularly be
satisfied by the corresponding media type. Any accesses for less than the listed amount of
data will suffer severe performance degradation. A value of zero indicates that the media
is in general suitable for supporting the small end of the system’s data access pattern.
• Minimum Virtual Volume Block Size is the smallest block size value that should be used
for the corresponding media type when physical volumes are combined to form a striped
virtual volume. A value smaller than that specified may result in severely degraded
performance whencompared to the anticipated performanceof the striped virtual volume.
• Note: When SCSI, SSA or Fibre Channel attached disks are combined to form striped
virtual volumes, the minimum access size should become—at a minimum—the stripe
width of the virtual volume multiplied by the virtual volume block size. If not, data access
will only use a subset of the striped disks and therefore not take full advantage of the
performance potential of the virtual volume.
2.9.1.12.2 Tape Media Parameters
Table 2-4 contains attributes settings for the supported tape storage media types.
Fibre Channel
Attached
4 KB 0 1 MB 1
Table 2-4 Suggested Block Sizes for Tape
Tape Type Media Block Size
Blocks Between
Tape Marks
Estimated Physical
Volume Size
Ampex DST-312 1 MB 1024 50, 150, 330 GB
Ampex DST-314 1 MB 1024 100, 300, 660 GB
IBM 3480 32 KB 512 200 MB
IBM 3490 32 KB 1024 400 MB
Table 2-3 Suggested Block Sizes for Disk
Disk Type
Media Block
Size
Minimum
Access Size
Minimum
Virtual Volume
Block Size
Notes