Backup, Backup and Backup Again

Protect your data, it’s not just part of your business it IS your business!

Backup never seems important until you have lost data. Backup hardware can seem expensive and if all goes well you will never see the benefits so it can appear to be dead money. That’s all well and good until something goes wrong and that workstation breaks down, you have a theft or worse still there is a fire and all of your equipment is destroyed. Even something simple like a gas main failing can prevent you accessing your data.

Data is the lifeblood of any company, you can replace computers, you can move to another office and you can hire new people but if you lose access to your data the company will, in most cases, fail. Think for a moment what it would be like to start your company again from scratch. You’ve lost all records of your customers and suppliers, you have no idea of any outstanding invoices, no idea of outstanding orders, no work that you may have had in progress, no previous projects that you can rework so everything has to be redone. You’ve lost all of that but you still have staff to pay, you still have bills coming in, you have to find the money to rent some office space, equipment and furniture, you still have customers expecting you to deliver. Insurance will cover some things but not loss of data, that’s why most businesses that have a disastrous event and don’t have a proper backup solution in place go to the wall.

Once you have a backup strategy worked out it is critical that you test it and ensure that you are capable of restoring from it. A backup is of no use to you if you cannot get at the data when you need it. Don’t keep your backup in the same place as the thing you are backing up. If you need to access the tapes you may not have access to the building that they are in or they may have gone up in smoke along with the server.

Legal considerations

Planning for a disaster is one very good reason to ensure that you have a good backup strategy but there are also legal reasons for you to ensure that you keep certain data. There are a number of regulatory frameworks that require that companies retain certain information for long periods of time. 

Traditionally, retaining data for regulatory reasons meant archiving paper copies of contracts, invoices, personnel records and so on but in many cases today there is no paper version. You may have emails between you and a customer that may constitute a contract. Somehow you need to be able to manage all of that data and once you start storing data electronically you then need to consider how you retrieve it should you receive a request under the Freedom of Information Act or the Data Protection Act. The National Archives has estimated that perhaps 25% of all emails could be defined as documents that should be retained unaltered.

RAID is not a backup!

I’ll get this one off my chest straight away, RAID is a great way of protecting yourself against equipment failure. If a hard drive in a RAID5 array fails you will not loose your data and all you have to do is replace that drive in order to restore your protection. So far, so good. What RAID does not protect you against is the user who inadvertently deletes a file and suddenly needs it again; the fire that burns down the building or the auditor who needs to see the customer approval that somebody thought they didn’t need anymore. Even if you have a RAID attached to your server you still need to back it up.

How much data do you have?

Consider what you want to back up and what you will need if you wanted to start over again. If you don’t have centralised storage and don’t use a workflow with version control there is a good chance that you have duplicates of files scattered across your network. A reasonable starting point would be to tot up the sizes of the user’s home folders on each of your machines and add in any servers or NAS devices that you may use. Don’t just think about how much data you need to back up today, consider how much you will need to be able to store in 18 months, 3 years or whatever period you would write off your investment in backup over.

How much changes each day?

It is important to remember that this means any file that has changed within that time and not just the amount of new files that are created, e.g. an Entourage mail database file can be up to 2GB in size and any time that Entourage is used this file will be changed and so will require backing up in it’s entirety. Since a user is likely to be accessing their mail on a daily basis Entourage will cause up to 2GB of data to be backed up every single day for each user if you are backing up each user’s home folder.

Remote users

Don’t forget your remote or mobile users. Laptops are very attractive to thieves so as well as securing the data on them you should ensure that you have a backup of it. If you use Mobile Homes you will always have a copy of the data on the server, where it can be backed up, but if you don’t there is another option. EMC Insignia’s Retrospect has a feature called Backup Server, which constantly monitors the network looking for computers that have not been backed up recently. If the computer appears on the network, for example when a mobile user is in the office or when a remote user connects to your VPN, the Backup Server will notice that it hasn’t been backed up recently and will start to back it up as soon as possible.

How long do you have to  back it up?

To be safe you should only backup data when it is not being used, effectively that means when all of your users have gone home for the day. If you never close you may have to take several “snapshots” of your data at various points during the day.

Grandfather-Father-Son Backup Technique 

A common backup scheme is known as Grandfather- Father-Son whereby once every 4 weeks you do a full backup (the Grandfather), reusing those tapes each year,  once a week you do a full backup (the Father), reusing  those tapes once every 4 weeks, and each day you do an incremental backup (the son), reusing those tapes once a week.

Using this scheme you can restore a system to an exact day within the past week, to within a week for the past 4 weeks and to within a month for the past year. You may need more granularity and so a more complex scheme will be required. In order to perform a Grandfather-Father-Son tape rotation you will require 14 periodical sets of full backup tapes, 3 weekly sets of full backup tapes and 4 daily differential backup sets of tapes to cover any changes that are made to files. If all of your data will fit on a single tape that still means you will need 21 tapes.

For most businesses a single tape is not adequate and it is quite normal to have a full backup that spans over 5 tapes with differential backups fitting on a single tape, which takes our tape requirements up to 89 tapes for an annual backup rotation. It is also sensible to make copies of each of the weekly and monthly tapes and to keep those in a separate location to the masters as tapes can be affected by environmental conditions.

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