[ale] Tape RAID?

[Greg Freemyer]

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?

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.

Greg
-- 
Greg Freemyer