Choosing and Setting Up External Media

There are a few choices regarding external media.

• External USB Hard Disks External disks can be connected directly to the RAID system with a maximum transfer speed of around 20 - 40MB/s, so expect long transfer times (about 4 hours for a 300GB disk). You can also connect disks to the control computers where the RAID set is NFS mounted, but this will be a lot slower (around 10MB/s, so a 300GB disk would fill in about 10 hours).

  Here are the steps to mounting an external USB disk. If mounting more than one disk, perform the steps below for each disk - don't connect all at the same time.

  • Connect to store1 It is currently possible to connect up to three external USB disks to store1. Use the two USB sockets at the back of the machine, and the top-left socket on the panel at the front.

  • Find /dev link

    Do

    ssh root@store1
    tail -f /var/log/messages
    

    This is the system log and in the last few lines you should see something like

    SCSI device sdb: 23442-byte hdwr sectors (120034 MB)
    

    The thing of interest here is sdb as this is the link to your USB disk (it could also be sdc, sdd etc). You can check the size and filesystem with

    fdisk -l /dev/sdb
    

    On the control machines, USB disks will simply be /dev/sda, /dev/sdb, etc (if partitioned it's /dev/sda1, /dev/sdb1, etc...).

  • Formatting (if necessary)

    If you need to format your disk, then do

    /sbin/mkfs.ext3 /dev/sdb

    This will format your disk with the Linux ext3 file system.

  • Mounting your disk

    To actually mount your disk, do (for example)

    mount /dev/sdb /mnt/hd1

    Now you can access your USB disk at /mnt/hd1.

  • Un-mounting your disk

    Before disconnecting the disk from store1, you must un-mount using

    umount /mnt/hd1

• ATABeast The SST has an ATABeast, which uses specially formatted hard disks. In order to use this storage method, your home institution would also need to have an ATABeast in order to read the data. Therefore this is not a practical storage solution for many.

  If you do choose this method, note that the ATABeast volumes are mounted under /beast on store1. For example, /beast/volume1

• DVDs Due to the large amount of data collected on an average day, DVDs are unsuitable as a storage medium. However, if you do wish to burn (lots of) DVDs, all the control computers are fitted with burners and the RAID set on store1 is NFS mounted on these machines also.