[ale] Tape RAID?

[James P. Kinney III]

On Mon, 2004-08-02 at 16:31, Greg Freemyer wrote:
> On Mon, 2004-08-02 at 16:24, James P. Kinney III wrote:
> 
> > I'm looking at an array of less expensive drives like the Ecrix gen 2
> > drive (still $1k but now does 12MB/sec). this won't come close to
> > saturating the U160 controller so hand 2 drives. The Ecrix drives can
> > also do variable speed writes by slowing the tape down if the need
> > arises.
> 
> The slow down feature is important.   Thanks for the info. I did not
> know anything but LTO had that feture.
> 
> > > 
> > > With that sort of speed, the issue is typically "how do I get data fast
> > > enough to keep the drive streaming?", not "how do I make the tape drive
> > > faster?".
> > 
> > Dual Gigabit ethernet!
> 
> Have you actually measured your backup needs, or are you just assuming
> the tape is the bottleneck?

At the moment, speed is not so much the issue as is the backup size.
Speed _will_ become the issue soon. I know the current tape setup is the
slow point as I can do a dump to a spare hard drive in a significantly
less amount of time as to the tape. I don't have hard numbers as I have
not set timers (next time I will).
> 
> I've done a fair amount of consulting in the backup area, and the issue
> is rarely the tape.  Normally it is the small size of the files and disk
> and/or disk fragmentation issues.
> 
> If your backup software will let you backup to /dev/null, try that and
> see how fast it runs.
> 
> HP recommends that a /dev/null type test be able to run at 2x to 3x the
> speed of your tape drive, otherwise the tape buffer will occasionally
> empty out and the shoe-shining mode will kick in.  Shoe-shining is
> _very_ slow.
No shoe-shinning with ecrix drives. They can slow to a stop and wait for
data.

Found a link to using RAIT under Amanda that looks very promising.
http://www.oops.co.at/AMANDA-docs/rait.html

> 
> Greg
-- 
James P. Kinney III          \Changing the mobile computing world/
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GPG ID: 829C6CA7 James P. Kinney III (M.S. Physics)
<jkinney at localnetsolutions.com>
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