Raid vs rsync -

[Bob Goodwin]

On 03/10/15 12:29, Gordon Messmer wrote:
> On 03/09/2015 11:04 AM, Bob Goodwin wrote:
>> However I have been wondering if it wouldn't work just as well to
>> periodically rsync the drive in use with a second drive?
>
> I know I'm going to repeat some of what has already been said.  My 2c 
> anyway:
>
> No, rsync would not work just as well.
>
> Do you want your system to continue functioning when one of your 
> drives fails? If so, then set up RAID1 and make sure you actually get 
> and read email from cron jobs.  In the event of failure, the mdmonitor 
> service will send email to "root" to indicate that a drive needs to be 
> replaced.  The down side is that your data will have no backups.  If a 
> file is accidentally deleted or corrupted, you probably have no recourse.
>
> Do you, instead, want multiple levels of online backups?  In that 
> case, there are a handful of backup applications, including rsnapshot, 
> that handle rotation and rsync to provide efficient backups.  If your 
> primary drive fails, you'll deal with the outage while you get a 
> replacement drive, format it, install a system, restore your data, 
> etc, which could be a fairly long process. Instead, you'll gain very 
> coarse file versions and protection from accidental deletions.
>
>> Am I going wrong somewhere in my thinking?
>
> Thinking that you have to make a choice between the two may be in 
> error.  Depending on the size of your disks and the amount of data on 
> them, you could potentially have both RAID1 and backups.
>
> Build a system with a RAID1 mirror on the two drives that uses half of 
> the available space for your system, and half of the space for a 
> separate backup filesystem.  Keeping the backup filesystem separate 
> provides some additional protection against filesystem corruption.  
> It's still possible for some errors to destroy both your system and 
> its backups, but in most cases, you'll get good coverage for the most 
> common failures with this setup.
.
Well as I said earlier, I mainly want to have files that I consider 
critical backed up somewhere. I'm not very much concerned about 
equipment failure and downtime. I've been backing stuff up between 
computers using rsync so that I'll always have a fairly recent copy of 
my notes, checking account, genealogy, etc.

Presently most of that data resides on a 1 TB drive in an NFS server 
running SL-6. I have two new WD/black 1 TB drives, that I am going to 
use on the computer I'm working on which is presently running Fedora-21, 
probably not the best choice for the purpose but I thought I'd try it.

I also have a Raid1 samba server [SL-7], mainly to deal with the family 
Apple users [everyone but me]. I have never received any messages from 
that. As it stands I might not know if there was a failure, I've been 
worrying about that!

I am considering everything in the responses I've received ...

Thanks,

Bob

-- 
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box10  Fedora-21/64bit Linux/XFCE