Per Jessen wrote:
Richard wrote:
Now, it isn't theoretical anymore. RAID is NOT a backup mechanism, good backups still are the only 'protection' for recovery of lost or damaged data, but RAID has convinced me that it is a pretty bulletproof HARDWARE solution for the reliability issue. It often *can* eliminate the need to actually use a backup because it helps prevent data damage in the first place (due to hardware, not pilot, errors) It is an integrity mechinism, not a backup mechanism, but if the harware is 'solid', and pilot error is removed, often backups never get used because the data is always available. Backups are primarily 'cockpit' error recovery, RAID does a great job of providing hardware protection against loss.
It's a slightly different topic, but running complete backups are far from always practical. The enormous amounts of disk-space and 24/7 production requirements make it virtually impossible to run complete backups. Backups are a last resort for when disaster strikes.
On my new server (2.7 TB RAID) I use LVM snapshots and rsnapshot on another disk as backup. Very fast and reliable.
So, it is no longer theoretical; you need RAID both on the primary AND backup hardware devices. That gives you the best fault tolerance, both human and hardware.
What do you do about the risk of a dual-drive failure? RAID6 is one possible answer, but AFAIK it requires at least 5 disks, which is too many (for my situation).
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