Backup is one (if not the) most boring subjects in the whole of IT.
- It looks simple
- It looks easy
If you are thinking this - then Backup/Restore have already got your IT system marked for a disaster.
Problem with backup
No-one likes doing Backup's for lots of reasons
- Takes time
- You need to be methodoical
- Need to be organised
- Easy - therefore "beneath me"
- Simple - only an idiot can get this wrong :)
Ah - yet more reasons to be very worried.
Reality of Backup
If you mess up
- Company goes bust
- Re-Pay bills
- Re-Order stuff
- Lost time/CPU Hours
Types Of Backup
There are basically 2 types of Backup
As often in IT there are good and bad things with each
Before I look at the types of Backup - you should be aware that there are generally 3 areas where you can backup to
- Software with Tape/Disk
In the movies - you may have seen old large tape drive - well they still exist - but now come in small Watch-Sized boxes. They are efficient - cheap - reliable.
Tape drives however do need maintenance - and occasionally go wrong.
You can also back up to Disk. This is the fastest, easiest to add to the system (tape drives can be driver specific - and troublesome). Disk drives however can fail - and adding RAID-5 to them adds more to your costs.
Software with Tape/Disk. As your Backup's get bigger - then the usefulness of Software defined backup increases. This extra functionalty however will cost you $$$$'s but save in your disk/tape spending.
|Tape||Been used for long time||Needs maintenance|
|Disk||Easy to add/Expand||Raid 5 more $$$|
|Software||Lessens the backup||Costs $$$|
This is the easiest way to do a backup
You have a Computer system
- Full Backup
- We are now OK ?
NO NO NO NO
You can not back up a live system and expect it to be rebuilt - the system devices/files/logs/password files etc on many Operating systems would not be compied correctly.
A full backup would only be suitable for a Data Directory/Files. And then only when the system is not being used.
The word incremental means "added to" - so an Incremental backup would only backup files that were added/modified (A directory would record that a file has been deleted).
This system is good - because it reduces the size of the backup's (after the first "Full Backup") - but if you then have 100 Increametal backups - and then your system fails. You will have to do a full restore - followed by 100 "Adds". The chances of this working well - are not good.
If you did a Full backup on Sat - and then 5 days incremental - this would be a better solution.
Usually most organisations have a
I do know however some places that use a 1 hour backup policy !!
1 Tape from the Daily "Pool" - gets added to the Weekly "Pool". Then At the end of the Month - 1 Tape from the Weekly "Pool" gets added to the Monthly Pool.
This mechanism is sometimes called GFS
GFS stands for
The #1 issue with backup is this
- Never Checked
- Never Tested
- How Long will this take ?
- London 1997 Bombing
2 Days you went broke
It may be working in Jan 2014.... but things are different in July 2015.... New directories/Disks - Has your backup been updated/Checked.
Even if the backup's are checked - have you really tried to restore ?
Hardware changes Spare Machines needed
Even if you have this - do you have time ?
- Developers do not like this work*
- Ops staff a best for this
Keep the tapes where ?
The Tapes (obviously you can not move the disks) should be kept in adifferent location.
So Machines in 1 Building - tapes should be in another.