Mailinglist Archive: opensuse (1695 mails)

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Re: [opensuse] 10.2 no RAID to 11.0 RAID 1
The backup has an advantage: you can recover from a software crash or finger
error: the other disk is not mounted, so nothing is written to it "yet". On
a raid, both copies would have the same wrong data.

The downside is that the machine is going to be a file/print/mail
server and while I may have a backup as of yesterday, if I screw up a
document, I cannot simply just restore the backup as other email would
have been added to the live mail server that would be lost if it was
restored from the offline backup.
I guess the way around that is to have two rsync jobs being one for
the mail directories and the other for only the document directories?

If you screw up a document, restore the document.
No one said you had to rsync the entire drive back.

In this scenario, the backup is just a mounted filesystem like any other and
you can copy individual files from it like any other directory.

Or am I missing some implication of what you said?

He did say one thing I guess which might have caused a confusion. When I do
this kind of thing, the backup disk IS mounted all the time, it's just mounted
as /backup or some other name that's out of the way of normal operations, not
part of a raid array getting updated every instant.
Or, if for some reason you want it to be unmounted normally, maybe so it spins
down and suffers less wear or maybe so an ungraceful shutdown dosn't harm it,
it's merely a "mount /backup" to mount it.

I don't happen to think there is any reason to dismount between backups. If a
power outtage happens, it will need to fsck during boot, but it will not
actually find any bad data because the fs was idle and the kernel flushes disk
buffers every N seconds (configurable). If the backup filesystem is reiser or
ext3 with journelling, then the fsck will not even take long. I suppose
unmounting could protect against more finger errors. Not impossible but less
likely to erase anything on an unmounted disk. Then again the damned
automounters that are on by default these days may place the backup disk
helpfully on the users desktop and atomout in /media/* just like thumb drives
and cameras, and so it's better to have it more statically configured and
mounted after all.

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Brian K. White brian@xxxxxxxxx http://www.myspace.com/KEYofR
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