HP B6960-96035 User Manual download pdf (Page 307)

The backup devices consist of an HP StorageWorks DLT 4115w Library as

well as two HP StorageWorks DAT24 autoloaders.

Why use the HP StorageWorks DLT 4115w Library?

The HP StorageWorks DLT 4115w Library has a single DLT4000 drive with

15 slots. It has a total compressed storage capacity of 600 GB and a maximum

sustained data transfer rate of 3 MB/s, or 10.5 GB/h, with data compression.

This is the transfer rate assumed for the remainder of this section. Currently,

the total amount of data to be backed up to the HP StorageWorks DLT 4115w

Library as a full backup, whether this is a single full backup, or the staggering

approach is used, is about 55 GB. Assuming that the size of an incremental

backup is approximately 5% of that of a full backup, a backup generation,

representing a full backup and all incremental backups based on this full

backup, requires (55+55*5%*5) GB, or 68.75 GB, of library space. In five

years time, this figure is projected to increase to about 210 GB. XYZ’s backup

policy requires that two backup generations of data be kept. Therefore, 210*2

GB, or 420 GB, of library space will be required for storage. The HP

StorageWorks DLT 4115w Library’s 600 GB storage capacity therefore

suffices.

Why use the HP StorageWorks DAT24 Autoloader?

The HP StorageWorks DAT24 autoloader has 6 24-GB data cartridges. It has

a total compressed storage capacity of 144 GB and a maximum sustained

data transfer rate of 2 MB/s, or 7 GB/h, with data compression. This is the

transfer rate assumed for the remainder of this section. Currently, the total

amount of data to be backed up to the HP StorageWorks DAT24 autoloader

connected to the aforementioned Windows 2000 client in the English

Department in a single full backup is 12 GB. Assuming that the size of an

incremental backup is approximately 5% of that of a full backup, a backup

generation, representing a full backup and all incremental backups based on

this full backup, requires (12+12*5%*5) GB, or 15 GB, of space. In five years

time, this figure is projected to increase to about 45 GB. XYZ’s backup policy

requires that two backup generations of data be kept. Therefore, 45*2 GB,

or 90 GB, of library space will be required for storage. The HP StorageWorks

DAT24 autoloader’s 144 GB storage capacity therefore suffices.

How long does a full backup last?

The Windows 2000 client in the English Department, which accounts for 12

GB of data is backed up locally to an HP StorageWorks DAT24 autoloader.

This device has a sustained data transfer rate of 2 MB/s, or approximately

7 GB/h. Therefore, a full backup of this Windows 2000 client takes about 2

hours. As the amount of data is growing at 20 to 25% per year, this client is

projected to hold about 36 GB of data in five years time. This data would

then be backed up in 6 hours.

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HP B6960-96035 User Manual Page 307