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. My previous article
outlines the steps that are needIf you are using BE 2010 or earlier. For BE 2012, you need to do the following
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
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.
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.
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.
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.