Chapter 1 – Overview
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The state of the offline file attribute for the three tiers of HSM is presented in the
following table.
Determining Disk Space Requirements
The Windows server (for example, the nTier700) must be configured with at least two
logical drives on magnetic disk—a boot drive (usually C:) and another logical drive
dedicated for use by the nTier File Migrator archive. The nTier File Migrator software is
installed on the boot drive but it requires minimal available capacity. The dedicated
logical drive stores file system metadata archive. This archive is used for read and write
caching of files held on tape and for storing all files that are retained online. This
dedicated logical drive must be formatted with NTFS and must be configured as a
dynamic disk.
Capacity requirements for the dedicated logical drive vary considerably depending on
how the system is configured. The total capacity requirement is the sum of the
following.
File system metadata
—Each file in the archive file system requires two NTFS
clusters. If the dedicated logical drive is formatted using the default cluster size of
4096 bytes, a file system with one million files will require 8 GB for the metadata.
Read and write caching
—The dedicated logical drive provides caching for each
file that is being written and all files that are open due to being read by a program.
Using a capacity allowance of twenty times the largest file size is adequate for most
environments.
Online Files
—Any group of files may be retained online. The administrator uses
the Archive Management Console to define policies for online retention. If tape
cartridge replication is not employed, the system can be configured to delete files
immediately after writing and reading, in which case the additional capacity
requirements for online files is zero. At the other extreme, the system can be
configured to keep all current files online, in which case the additional capacity
requirements for online files is the sum of all the file sizes within the file system.
HSM Tier
Description
Offline Attribute
Online
One instance of the file is on magnetic disk and, in addition,
there may be one or more instances on tape.
Not set
Nearline
At least one instance of the file is on tape within a tape library or
tape drive and no instance is on magnetic disk.
Set
Offline
The file is not stored on magnetic disk and the instances on tape,
all of which have been exported from the tape libraries or ejected
from stand-alone drives.
Set