RAID question

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What happens if a RAID drive (Sata drive) fails? I set up my first
RAID system ever. I have 4 Sata drives, all identical 500GB drives. I
set them up as a RAID 1+0 (mirrored and striped), Windows XP. They now
appear as a dynamic drive in WinXP that is 750GB.  But I do not
understand what will happen in the future when one of the drives
fails? Would I need to have a 5th identical drive on hand to replace
the drive that fails? What if I do NOT have a 5th identical drive on
hand in the future, then what are my options in the even of failure of
one of the drives? Would I be better off setting up a RAID0 (for
speed, which is my primary need, to play back 1920x1080 high
definition video I am editing) with just two of the Sata drives, keep
the other two Sata drives as plain old Sata data drives, so they would
be available in the future to repair a damaged RAID0 that might occur?
Any help or instruction to this RAID noobie greatly appreciated.

Re: RAID question

randall_o wrote:
Quoted text here. Click to load it

I think another question you could ask, is how much bandwidth is
really required. For example, the Performance snap-in in the Administration
tools, can be used to record bytes/sec of I/O, and you can use that
to see how much bandwidth is taken by your editing application. Another
tool that can do something like that, is the Sysinternals Process

Maybe even RAID0 is overkill. Set up a demanding edit set of conditions,
and see what it takes to render or whatever.

With RAID0+1 or RAID10, a fifth drive is a useful thing to have in
the room. It means relatively little downtime, to set up the spare,
and do a rebuild. And with the RAID management software, you should
be able to do the rebuild, while Windows is running.

RAID0 has no redundancy, so you want a second copy of the work
files, on one of your other drives. If one of the RAID0 disks
is lost, the data is lost. RAID0+1 or RAID10, are there to provide
redundancy to a RAID0 situation, so all is not lost if one disk

The best way to handle RAID is

1) Put Windows on a separate hard drive. This avoids the situation
    where the RAID fails, and you can no longer boot. This happens to
    some people who set up RAID5 and suffer a no-boot situation, when
    it really should have been able to boot.
2) Put whatever else you want on the RAID array.
3) Practice doing maintenance on the RAID array, with only a
    couple test files on it. If you do something stupid while
    practicing, nothing is lost (like, say, changing array
    types and everything gets erased). Once you become proficient
    at changing to the fifth disk or whatever, then it is time to
    stage real data on there. Disconnecting the fourth drive, is
    enough to simulate a failure. While you're doing the experiments,
    you may even manage to figure out the physical relationship between
    SATA ports, and where the failure is declared in the RAID interface.
    (That makes it easier to figure out what drive to pull in a
    real emergency.)
4) RAID is not a backup strategy. Say the power supply feeding
    your four drives, decides to deliver 15VDC to the motors on the
    hard drives, burning all four of them. Now, your data is lost.
    Having a separate drive, with a backup copy on it, is worth its
    weight in gold. If that storage is located on another computer,
    and physically separated from your current computer, that improves
    the odds that the backup will survive some kind of accident.

If it was my setup, the first thing I'd test, is the bandwidth requirement
of the editing setup. While a major movie studio setup may need
150MB/sec for their HD, many home setups used compressed formats,
so that the overall datarate involved is not that great.


Re: RAID question

Thank you Paul. Excellent advice and tutorial, answers a lot of my
questions. Excellent point about RAID not being a backup solution;
that alone might change my mind about RAID10 so that I just do a two
disc RAID0 to get the bandwidth (I need it, I already tried playback
of a 1920x1080 rendered video clip and it was jerky when played
straight off one of the Sata drives prior to setting up RAID; and this
is a dual core 4GB system, high end nvidia graphics card, etc).  I
guess RAID0 with two discs is looking good (just for short films for
now, so I do not need mega disc space RAID yet, as would be needed for
feature film editing and rendered playback). Editing is not problem,
that goes great even on the current 100GB ide drive that has WinXP and
Sony Vegas Pro 8 editing software. It is the playback of high
definition (blu ray quality resolution) rendered video clips that is a
problem; thus the need for RAID0.  I think RAID0 and some other backup
system physically separated from the RAID is a good idea as you said,
much thanks.

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