Disk Swap Policy

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The policy, like any 'insurance' policy, must start with you deciding what is the 'affordable' loss of data in case of fire, flood, theft, or accidental damage i.e. a situation leaving you without a GEM and its two disks. This is what disk swapping is protecting you from.

  • Do not remove the top disk.
  • Only swap the lower disk – the backup disk.
  • Data corruption may occur if you remove the top disk while the power is on.
  • Do not swap the disk at 02:00 hours as this is when the backup starts*
  • The Swap Policy depends on your requirements. Here are some pointers.

1) The 'off-site' disk contains the version of the data from the last night it was in. So if you swap once a week (say - Friday 5pm) then you have an off-site copy that represents the state of play from Thursday evening. Also for some specific items we can add extra 'snapshots' during the day so this disk would also have some data from Friday.

This is how the majority of GEM owners operate. The general assumption is, if your office goes up in smoke, then at worst, you go back a week.

2) If you swap every day, then at night, you have an off-site disk with data that is about 24 hours out of date. This sounds better, however during the day you have no offsite disk at all, unless you can keep the disk elsewhere and only fetch it to make a quick change. There is also the option of a secure, fireproof safe.

So we recommend to all users that if an ‘every day swap' is planned you should have a total of four disks. This way one of the disks is always off the premises. In other words we strongly recommend that one of your disks is kept as far from your office as possible for as much time as possible.

3) We recommend that the disk swap is done at the end of the day. The main reasons being:

a) This way the files from the previous day are always available instantly. They are on the disk that was in the machine last night.

b) If any 'snapshots' are set-up (i.e. frequent backup of critical files) then the disk you remove at the end of the working day, will contain the most recent version.

c) On rare occasions, the system needs to perform full checks and scans of the newly inserted disk. This can take some time and makes the system sluggish and unresponsive. If this happens at the end of the day, it is usually not a problem.

*Maximum achievable backup speed is 1GB in 20 seconds however this will not be seen in practice. Cataloguing of files before a backup is a factor in the time taken to complete the backup. Your backup notification e-mail will show you this data.

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