JohnC
December 5, 2002, 05:42 pm
Backups
Every system should be backed up – everyone knows that, but how many people actually do it? It really is no use skimping because of things like ‘tape cost’ or ‘can’t afford the time’ because when the system goes down (when, not if). And it’s not just systems going down – it’s mistakes by people who want to revert to a previous version of their document/program/picture because they themselves have made a bit of a hash of doing something. And it’s the cost of redoing something or everything that should be taken into account when balancing the cost of backup infrastructure against not doing backups.
In my mind there are two scenarios of backup, the home or very small business running on a small number of PCs, and the network, which is anything larger. To quantify very small, let’s say (number_of_PCs<4).
The Home or Very Small Business.
The vast majority of PCs these days have CDRW drives. So just before you go home or finish for the day take a copy of what you’ve done. It needn’t take long. Then take the CD off the premises with you – if you’re at work. Or take it to work with you if you’re at home. If you can do neither, try to arrange a swap store with a friend. All you want is somewhere outside the premises so that if in the very unlikely event of a fire or other destructive activity (burglary?) as well as pure system failure so that you are not reliant on the physical security of the premises.
What to back up
Ideally, all your data every time. This is, however, impracticable for CDs only in the amount of time it would take. If you have tape backup then it’s different, and that’s tackled in the larger network section below. CDRs are cheap, compared with the cost of not having the data. CD/RWs are relatively cheap, and have the advantage of reusability. A decent quality CD will have a life of 30+ years of stored correctly so CD backups are, to all intents, safe. If the “all data” option is not open to you then you have to make judgements about what you’ve just changed – for instance an address book or database would be backed up more frequently than a set of photos, which should have their own CD set that’s stored in the dark and cool. More detail than this is not appropriate here – you’ll have to read up on the subject. But above all, label your CDs – the CDs themselves, not the cases. See below for labelling and cycling schemes.
The Network Backup
You should really have a tape drive – what type is unimportant but it should have a reasonable capacity, otherwise you’ll be changing tapes ad infinitum. You can back up multiple machines to the single tape. If you’re worried about operating system costs then Linux machines back up Windows machines very successfully. But you have to get organised.
Labeling Backups
Label the tapes with machine name and cycle number. Don’t, as I’ve seen, just rely on coloured dots on the cases because they wanted to keep the tapes tidy. Anonymous tapes result. Which is OK until you take two tapes out of their respective cases. Then you don’t know where you are.
Making Backups
Windows NT/2k/XP servers/workstations have their own backup programs – learn how to use them. You can also schedule backups for any time of night so that you can leave them unattended. Win 9x/ME do not – you have to install software. But once this is installed you can start. You can choose a complete or some sort of incremental backup procedure – either files changed since last full backup or files changed since last incremental backup. I’ve given below my suggested schemes.
Backup Cycling
It used to be the case, 20 years ago then Grandfather, Father, Son was the accepted norm – i.e. a cycle of three backups. This is now no longer acceptable and some more safety is required. I used to maintain two cycles of backup – Developer backup and Accounting backup, depending on the application.
Developer backup uses fifteen tapes and was based on a rolling two week cycle, with substitutes of Fridays in weeks three and four. The last day of the month was a separate four monthly rolling cycle.
Thus:
Week 1 - Mo1, Tu1, We1, Th1, Fr1
Week 2 – Mo2, Tu2, We2, Th2, Fr2
Week 3 - Mo1, Tu1, We1, Th1, Fr3
Week 4 – Mo2, Tu2, We2, Th2, Fr4
Month End – Jan/Apr/Jul/Oct, Feb/Mar/Aug/Nov, Mar/Jun/Sep/Dec
The month end is substituted as appropriate.
Accounting Backup
Thus:
First Year
22 tapes used sequentially each working day of the month
12 tapes one for each month end
Second Year
The same 22 tapes used sequentially each working day of the month
A different set of 12 tapes one for each month end
Third Year
Revert to Year 1 tapes
So that all this become clearer I’ve prepared an Excel spreadsheet for 2003 that is downloadable from http://www.colbyweb.co.uk/backup/backupsched.xls
These are only two schemes – there are many more – but they’ve worked for me over a five year period.
Full or partial backups?
You have to decide, based on the size of your tape drive, the schedule you can follow. If you have enough tape room, it make sense to do full backups. If you don’t then work out a schedule. But don’t skimp, and change tapes at the recommended time – like every couple of years. It may cost but not as much as losing everything. And buy a cleaning tape – you’ll need it.
That’s it, really.
Backup Stories from the Support Desk
1) “We haven’t done a backup, we haven’t finished entering all the data yet.” (on system setup which failed)
2) Support – “We don’t know what’s going on, can you send us copies of your disk please.” Photocopies of said disks arrived in the post.
3) On site “Have you filed your backups?” “Yes they’re here” – indicating lever arch files with about 20 8 inch disks that had been carefully hole punched and filed.
4) Call to support desk “Our system fell over, so we took all three backup copies.”
Every system should be backed up – everyone knows that, but how many people actually do it? It really is no use skimping because of things like ‘tape cost’ or ‘can’t afford the time’ because when the system goes down (when, not if). And it’s not just systems going down – it’s mistakes by people who want to revert to a previous version of their document/program/picture because they themselves have made a bit of a hash of doing something. And it’s the cost of redoing something or everything that should be taken into account when balancing the cost of backup infrastructure against not doing backups.
In my mind there are two scenarios of backup, the home or very small business running on a small number of PCs, and the network, which is anything larger. To quantify very small, let’s say (number_of_PCs<4).
The Home or Very Small Business.
The vast majority of PCs these days have CDRW drives. So just before you go home or finish for the day take a copy of what you’ve done. It needn’t take long. Then take the CD off the premises with you – if you’re at work. Or take it to work with you if you’re at home. If you can do neither, try to arrange a swap store with a friend. All you want is somewhere outside the premises so that if in the very unlikely event of a fire or other destructive activity (burglary?) as well as pure system failure so that you are not reliant on the physical security of the premises.
What to back up
Ideally, all your data every time. This is, however, impracticable for CDs only in the amount of time it would take. If you have tape backup then it’s different, and that’s tackled in the larger network section below. CDRs are cheap, compared with the cost of not having the data. CD/RWs are relatively cheap, and have the advantage of reusability. A decent quality CD will have a life of 30+ years of stored correctly so CD backups are, to all intents, safe. If the “all data” option is not open to you then you have to make judgements about what you’ve just changed – for instance an address book or database would be backed up more frequently than a set of photos, which should have their own CD set that’s stored in the dark and cool. More detail than this is not appropriate here – you’ll have to read up on the subject. But above all, label your CDs – the CDs themselves, not the cases. See below for labelling and cycling schemes.
The Network Backup
You should really have a tape drive – what type is unimportant but it should have a reasonable capacity, otherwise you’ll be changing tapes ad infinitum. You can back up multiple machines to the single tape. If you’re worried about operating system costs then Linux machines back up Windows machines very successfully. But you have to get organised.
Labeling Backups
Label the tapes with machine name and cycle number. Don’t, as I’ve seen, just rely on coloured dots on the cases because they wanted to keep the tapes tidy. Anonymous tapes result. Which is OK until you take two tapes out of their respective cases. Then you don’t know where you are.
Making Backups
Windows NT/2k/XP servers/workstations have their own backup programs – learn how to use them. You can also schedule backups for any time of night so that you can leave them unattended. Win 9x/ME do not – you have to install software. But once this is installed you can start. You can choose a complete or some sort of incremental backup procedure – either files changed since last full backup or files changed since last incremental backup. I’ve given below my suggested schemes.
Backup Cycling
It used to be the case, 20 years ago then Grandfather, Father, Son was the accepted norm – i.e. a cycle of three backups. This is now no longer acceptable and some more safety is required. I used to maintain two cycles of backup – Developer backup and Accounting backup, depending on the application.
Developer backup uses fifteen tapes and was based on a rolling two week cycle, with substitutes of Fridays in weeks three and four. The last day of the month was a separate four monthly rolling cycle.
Thus:
Week 1 - Mo1, Tu1, We1, Th1, Fr1
Week 2 – Mo2, Tu2, We2, Th2, Fr2
Week 3 - Mo1, Tu1, We1, Th1, Fr3
Week 4 – Mo2, Tu2, We2, Th2, Fr4
Month End – Jan/Apr/Jul/Oct, Feb/Mar/Aug/Nov, Mar/Jun/Sep/Dec
The month end is substituted as appropriate.
Accounting Backup
Thus:
First Year
22 tapes used sequentially each working day of the month
12 tapes one for each month end
Second Year
The same 22 tapes used sequentially each working day of the month
A different set of 12 tapes one for each month end
Third Year
Revert to Year 1 tapes
So that all this become clearer I’ve prepared an Excel spreadsheet for 2003 that is downloadable from http://www.colbyweb.co.uk/backup/backupsched.xls
These are only two schemes – there are many more – but they’ve worked for me over a five year period.
Full or partial backups?
You have to decide, based on the size of your tape drive, the schedule you can follow. If you have enough tape room, it make sense to do full backups. If you don’t then work out a schedule. But don’t skimp, and change tapes at the recommended time – like every couple of years. It may cost but not as much as losing everything. And buy a cleaning tape – you’ll need it.
That’s it, really.
Backup Stories from the Support Desk
1) “We haven’t done a backup, we haven’t finished entering all the data yet.” (on system setup which failed)
2) Support – “We don’t know what’s going on, can you send us copies of your disk please.” Photocopies of said disks arrived in the post.
3) On site “Have you filed your backups?” “Yes they’re here” – indicating lever arch files with about 20 8 inch disks that had been carefully hole punched and filed.
4) Call to support desk “Our system fell over, so we took all three backup copies.”