On Wed, Dec 20, 2017 at 05:26:57PM +0000, Mark Rogers wrote:
On 20 December 2017 at 17:07, Chris Green cl@isbd.net wrote:
I've never really seen any need for RAID on a home system. I make sure everything is safely backed up and go with the OS on an SSD and /home on a big rotating one.
Preaching to the choir I am sure, but anyway:
If you have adequate backups and uptime isn't important then yes, RAID is unnecessary. As long as you remember that any data stored only in one place isn't a backup, it's an archive (unless it's your live working copy).
Eg: You backup incrementally daily to a second disk. It includes yesterday's copy of a project you're working on, the day before's, etc. Each of those historic files, unless they're unchanged subsequently, only now exist in that one place, so if that disk fails and you then need to roll back you can't.
It may be sufficiently unlikely to not worry about it, but as long as that's a judgement made that's fine. Personally I'd have my backups on RAID even if my main drives aren't (unless they're duplicated elsewhere, eg to the cloud).
Too many people "back things up" onto an external drive so that they can delete them from their laptop to free up space, without understanding that they're no longer backups once you delete the original copy.
All correct. :-)
My short-term incremental backup is to a separate disk drive on the same machine, covers hourly + a few days daily.
My long-term incremental backup is daily and back for a year or more to another machine in a different building.
Yes, if one of these dies then I don't have the backup but I only need the backup if something goes wrong and with two 'layers' I'm happy that I can recover mostof what I need in case of catastrophe.
The only drive I've had die within the last few years was the short-term backup one which lives in my desktop server. It wasn't *totally* dead so I simply copied what was OK onto a new drive and carried on. Even if it had been totally dead all I would have lost would have been incremental backups for the past few hours.
To date I've only once lost a hard disk that I couldn't recover data I needed from. (I thought we had a backup but it turned out that wasn't the case.) On that occassion I used a data recovery service and they got everything back (the disk wouldn't even spin up for me; prior to that I'd usually been successful with testdisk/photorec/scalpel/etc). It cost me £500-ish.
But one day I'm going to have a catastrophic failure and be glad I do generally have backups. Or rather upset when it turns out they're not working the way I expect. (Another truism: A backup that's not tested isn't a backup.)
Yes, my backups get tested fairly regularly either when I delete a file (or change it) and want to get back to a few hours ago or when someone else in the family says "can you get file xyz.abc from last year".