RAID Disk Space in Web Hosting
There's often confusion over the role RAID plays in web hosting with some getting confused between the protection against disk failure offered by RAID and a true backup solution, the following text attempts to try and clarify this.
What RAID Is Not
RAID is not a backup solution.
RAID disk space does not offer an alternative to a proper backup strategy as it does not offer any protection against accidental or malicious deletion of files, once a file is deleted from a RAID array that file has gone.
A RAID array also offers no protection against a bug in the operating system corrupting all the data on the array nor does it offer protection against catastrophic failure of the server.
What RAID Does Do
There are many different RAID options available each with their own benefits and weaknesses, however for the purposes of this text we can assume we are only referring to those modes that provide redundancy.
A RAID array configured for redundancy will allow a single drive to fail in the array without causing the server to stop due to the failed drive, also there will be no loss of data. The failed drive can then be replaced with a new working unit and the array rebuilt to its full operational state.
The RAID array helps to minimise downtime as the server needs to only be offline for the time taken to replace the drive, if RAID isn't used and the drive fails then the server would be offline for the time it takes to replace the failed drive, reload the operating system and restore the backups a process that can take several hours.
It should be noted that a RAID array must be monitored as once a drive fails the array is generally no longer able to provide redundancy so should another disk fail the degraded array will offer no more protection than a single drive.
Summary
RAID arrays are good at helping to improve uptime by reducing the maintenance time in the case of a drive failure, however they are no substitute for a well thought out backup strategy.
- TOLRA uses a combination of RAID arrays for redundancy and Continuous Data Protection to provide backups with a rotation schedule.
- TOLRA actively monitors the health of the arrays on all servers.
