OPC IT. Managed services and web development in Canberra.

Backups vs Snapshots vs Replication

Date: 
21 August 2014
Authored by: 
Jason Hayes

There can often be some confusion between the difference between Snapshots, Backups (Off-site backup) and Replication.

Snapshots

Snapshot are simply a freeze frame of your data or a 'photo in time' of the server/data. Snapshots are used when you need to complete Windows updates or install new software on the server. This allows the administrator to wind back the clock if an issue occurs with the upgrade or update quickly without having to restore the whole server.

Snapshots can start to impact production performance if left for too long as the data changes significantly from what is in the snapshot. This can cause major outages if left as the server storage can run out of space and crash all servers on the array and make it incredibly hard to get everything back up and running again.

As a rule, snapshots are only used as a last resort; you should not be using snapshots as backups.

Backups

off-host backup is simply when you take a copy of the server/data to a device which can be taken offsite, e.g. a tape or an external USB drive. This is important because if the host or storage array fails you will need a good recent backup to restore from.

I would consider backups as the most important part of IT these days. If the amount of data being backed up is relatively small then you can get away with completing full daily backups. However, as data grows the amount of data being backed up can get quite large. If this is the case, what you will find is most organisations will complete a full backup of their data, say, on a weekend, and then incremental backups of their data throughout the week. This allows the backups to be completed before the start of the next day so no data is missed when the next backup is run.

I won’t go into all the different ways to do a backup and store a backup, but suffice to say, a backup copy is incredibly important!

Replication 

Replication is where you use a piece of software to replicate your server(s)/data to another piece of the server(s) or storage hardware. I find this the best way to protect your business as the replication of the data is generally offsite (if setup correctly).

If one site goes down, the other can be powered up with the most recent version of data that has been continuously copied from the production data. It is not intended to be used as a backup copy but can be in certain situations where a daily backup has failed due to a tape not being changed (it has happened before, and will continue to happen in the future!)   

Some issues with replication is if the system is setup to replicate the data hourly, a problem that may not have been picked up straight away can be replicated to your offsite location which could leave your replication copy with the same errors. This is why it is important to try and have multiple backups.

If you find you are in a situation where you need to restore data, backups are your last line of defence. Remember a full backup can be restored to another piece of hardware anywhere. Don’t ever rely on just one copy and if you are facing a restore of a sever or data, before trying to restore anything, backup your backup!