Mark (aka Storagezilla) Twomey wrote in his blog last week about copies and backups, and concluded that point in time copies are backups.
Hrmm. As I have said before, I am not sure that I agree with this.
I have discussed the issue here with W. Curtis Preston too, and I think there is a disconnect happening somewhere. I am fundamentally uneasy with the idea of calling a copy a backup. It seems to me that a copy is a necessary part of a backup, but not sufficient.
Would a tar ball be a backup? A gzip?
Again, I think the answer is, at best, "sort of".
And why do I differentiate between a copy and the tar ball?
Because I think there is not only a difference between copies and backups, but I think there is a difference between a backup and a backup and recovery system.
So lets start with fundamentals.
SNIA has this to say regarding the definition of a backup:
backup 1. [Data Recovery] A collection of data stored on (usually removable) non-volatile storage media for purposes of recovery in case the original copy of data is lost or becomes inaccessible; also called a backup copy. 2. [Data Recovery] The act of creating a backup. See archive.
SNIA also notes that: "To be useful for recovery, a backup must be made by copying the source data image when it is in a consistent state."
- A definition for backup
- A definition for backup and recovery process or system
- A set of mandatory requirements for a backup (included in the definition) and a set of desirable requirements (not included in the definition)
- A set of mandatory requirements for a backup and recovery system (included in the definition) and a set of desirable requirements (not included in the definition)