Credit: Post based on CISSP course presented by Dennis Lee, November 2018
Welcome to February 2021! This month I plan to wrap up our CISSP blog post series.
Let’s start by talking about data backups! There are lots of ways to do data backups:
- A Full backup is exactly what it sounds like – all your data is copied to another location and backed up.
- A Differential backup is where all data that’s changed since the last full backup is copied.
- An Incremental backup is where all data that has changed since the last full OR incremental backup, is backed up. This is easier to restore from but you will need more time and media storage space.
Some technology that can be useful for creating backups is a Redundant Array of Independent Disks (aka RAID). Again, lots of choices:
RAID 0 – Stripping of data – very fast, no recovery! 2 drives minimum required.
RAID 1 – Mirroring – double storage cost, slower, 2 drives minimum required.
RAID 3 & 4 – RAID 3 reads and writes data at the byte level. RAID 4 reads and writes at the block level. You can only lose 1 active drive at a time. If the parity drive fails, the RAID falls back to RAID 0 or you can rebuild the parity drive back on a spare drive. This requires 3 drives minimum and only gives 2 drive capacity.
RAID 5 is faster because parity info is written in parallel. If there is no spare drive, it will reconstruct lost data and parity info into system memory in chunks. It needs 3 drives minimum, with a 2 drive capacity.
RAID 6 (Enhanced RAID 5) provides 2-dimensional parity, allowing for the loss of 2 drives simultaneously. It needs 1 extra drive than a RAID 5. Requires 4 drives minimum, with a 2 drive capacity.
You can also combine RAID’s: e.g. 0+1, 1+0, 1+5, 5+1, etc.
Excellent Tips 