External hardisks, whether they are USB or
eSata, are increasingly used as backup media, in place of tapes. If you
are using more than one external harddisks, you would want to set them
up so that there are minimal adminstration after the initial set-up.
You should be able to swap disks without having to modify your backup
jobs. For BE 2012, you need to do the following

1) Define storage on your external harddisks.
Plug in your harddisk(s) and in the Storage tab,
click on the Define Storage button. Follow the steps to define disk
storage on your external harddisk. If your disks are recognised as
fixed disk by the OS, then you can only define Disk Storage on them.
Otherwise, define Disk Cartridge Device on them.
Don't worry about the drive letter that the disk
is assigned. BE will be able to handle any changes in drive letters
later on. Do not assign a fixed drive letter to the disks.
Give your storage a name such that from the BE console you can
identify which disk is connected to the media server. See my screenshot
below.
This is the crucial step in the whole process, so don't get it wrong. Make sure that you DEFINE ONE STORAGE PER DISK.
If you have sufficient ports, plug in all your external harddisk at
the same time before you start defining storage. This is to ensure that
each harddisk is recognised by BE as seperate harddisks. When you
unplug and plug in the harddisk, the corresponding storage should go
off-line and on-line accordingly.
If you don't have to sufficient ports to plug in
all your disks at once, then make sure your previously defined storage
do not come on-line when you plug in a new disk. For example, you
defined "Disk Storage - USB Disk 1" on your USB Disk 1. When you unplug
USB Disk 1, "Disk Storage - USB Disk 1" goes off-line, as expected.
When you plug in USB Disk 2, "Disk Storage - USB Disk 1" came on-line
so you are unable to define any storage on USB Disk 2. This could
happen if the diskid of the two USB disks are the same. BE tracks disks
by their diskids. If you encounter this situation, check and change
the diskids using the procedure below
https://www-secure.symantec.com/connect/blogs/changing-diskid
Make sure that your disks have different diskids.
If the diskids of your disks are not the same and the storage defined
on one disk comes on-line when another disk is plugged in, re-start all
your BE services. As I said before, make sure that you define one
storage per disk. Do not use one storage for all your disks.
2) Define a storage device pool.
Click on the Define Storage button and select Storage Pool
Follow the dialog and add the storage that was defined in Step 1 into the pool
Even though you have only storage on your external
harddisks, you should not skip this step and use the All Disk Storage
device pool. This is because the All Disk Storage pool is a catch-all
pool. If later on, you define a disk storage on an internal disk or
another external disk which is not part of this set of disks. It will
automatically be included in the All Disk Storage device pool. This
will mess up your backup when the backup sets goes onto the disk storage
on your other disks.
3) Define a job
Define a job and target it to the storage pool that you have created in Step 2.
This job will then write to whichever disk in your set of disks that is plugged in and is on-line at the time of the backup.
Good Practice
In BE 2012, the backup chain is very important. A
backup chain is the set of backups that are necessary for recovery to a
certain point-in-time. For example, if you do a full backup on
Friddays and increment backups on Mondays to Thursday, then the set of
backups from Friday to Thursday is a backup chain. If you decide to
restore from the Thursday incremental backup, BE 2012 is smart enough to
restore the last Friday's full backup and then the incremental backups
from Monday to Thursday automatically. Hence it is a good practice to
keep the entire chain on one disk. In this case, it is good practice to
rotate the disk only on Friday before the next full backup. If you
rotate the disks every day in this example, then you would be scattering
the backup chain amongst all your disks. This will be a hindrance when
it come time to do a restore.
Also, if you are using Disk Storage, DLM will be
managing your disks and it grooms entire backup chains at once, not
individual backup sets. Again, for this reason, it is good to keep the
entire backup chain on one disk.
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