Backing up RAID

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masteraleph

Limp Gawd
Joined
Jun 22, 2005
Messages
435
Yes, I know, RAID is not a backup. Therefore, my question is- how difficult is it to back up a RAID array?
 
For home users, the answer is generally "another raid array", or some sort of hard drive setup. Tape is expensive and DVD is inconvenient.
 
unhappy_mage said:
For home users, the answer is generally "another raid array", or some sort of hard drive setup. Tape is expensive and DVD is inconvenient.
Click to expand...

Right, sorry, I didn't ask the question very well-

For good reason, it'd be some sort of HDD backup. The question is- would it have to be another RAID array? Say you have a RAID array totalling 1TB of storage (excluding redundant storage within the array)- could you back up to a 1TB HDD? For that matter, let's say that there's a 1.5TB array, but it only has 300GB of data- would there be automated software to back up the 300GB to a single HDD?
 
rsync

The problem with your solution is that silent corruption of data will see you overwrite the good backup with the bad data before you recognize the problem.

That's why tapes are valuable, you can shelf them once a week.
 
The point of raid 5 is to provide some level of protection and uptime during a single drive failure. That is it. As mentioned above a true backup is seperate on another system.

Fortunately, I doubt many of us DON'T have more than a few 100GB of "real" data that "needs" to be backed up. I would highly recommend finding and online webhost that gives a few 100GB for less than $100/year. Then get a program like syncbackupSE to keep your "real data" safe and offsite. If you want an extra level of protection get a external dive and copy your critical to it twice (two seperate directories), unplug it, and take it somewhere else. Between online, your local drives, and a copy offsite you really don't need raid 5 other than for uptime (which isn't a bad thing).
 
masteraleph said:
The question is- would it have to be another RAID array? Say you have a RAID array totalling 1TB of storage (excluding redundant storage within the array)- could you back up to a 1TB HDD? For that matter, let's say that there's a 1.5TB array, but it only has 300GB of data- would there be automated software to back up the 300GB to a single HDD?
Click to expand...

To simplify: If you can copy a file somewhere, it's a backup. Extend to directories and recurse, and you've got a complete backup of all but the pesky boot sector and other such hidden info. Separate your OS and data onto separate drives/arrays, and that problem gets reduced significantly.

Backup software is free to use any encoding of the data it wants, whether to single file archives or not, but as a general rule, they operate on top of file systems, therefore don't care so much about the underlying media and its sizing, beyond the need for sufficient storage for its needs. As you don't need a 1 TB drive to store a 1 KB file, you don't need a 1 TB drive to backup a 1 TB array holding only 300 GB of data.

There are some backups which are strongly tied to particular media and sizing, e.g. full drive imaging, but the point here is that not all backups are such exceptions, so you can use file system level thinking to help you out here.
 
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