Re: Software RAID and drive failures
On Sat, 2003-03-08 at 13:40, Juhan Kundla wrote:
> Hei!
>
> I apologise, that i bother you with questions, that are not entirely
> Debian specific. I don't know any better place to ask those questions.
> If someone here could point a newbie like me to right direction, it
> would be very much appreciated.
>
> I have a task to set up a file server. I have very small budget but
> quite high demands for data integrity. I must do everything possible to
> ensure, that i can recover data after hardware or user failures.
> The performance of the computer is not very important.
Ah, asking for the impossible, are we?
> There is no way i could buy expensive hardware (SCSI and tape drives are
> really not an option). I think i can afford two or three IDE disks. So
> here is my plan.
How much capacity do you need?
> I buy two smaller (and cheaper) IDE disks and use them in RAID-1 array.
> I hope that this gives me good protection against hardware failures. If
> one disk fails, then other will still have my data intact, right? The
> main question is, that how good is the software RAID, when one drive is
> not lost completely, but it starts to have more and more bad blocks?
> Will the RAID-1 protect me from data corruption in that case? Any
> comments?
Here's where expensive SCSI disks and controllers are helpful: they will
tell you when a disk starts to act up.
> I know, i still have to take backups, because the RAID and mirroring
> won't protect me against other types of failures. I was thinking about
> using a separate much bigger IDE disk for backups. If the backup drive
> would be 7 times bigger than those smaller disks, then i could take a
> full backup every weekday and have seven copies of my data, every copy
> taken in different time. This gives me maximum one week to react to data
> loss or corruption and if i accidently deleted wrong files, i would
> could restore them from backup, that is not older than 24 hours.
You probably don't need to back up the whole disk every day, do you?
Backing up /home, /etc and the data directories each day is, of course,
mandatory, but backing up "static" data, like, basically, everything
else would only have to be done after you to an "apt-get upgrade" or
"apt-get install".
That way, you don't need to back up as much each night, and using
tar + bzip2 would make things even smaller.
Unfortunately, an electrical surge might fry your "backup disk", which
would mean you have no backups at all.
I'd get an external USB or firewire drive, and physically disconnect the
drive and remove it from the premises after the backup.
> So what do you think, is my plan plain stupid, or does this really give
> me some protection against data loss. Should i investigate any other
> technologies? EVMS?
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