> -----Original Message-----
> From: veritas-bu-bounces at mailman.eng.auburn.edu
> [mailto:veritas-bu-bounces at mailman.eng.auburn.edu] On Behalf
> Of Joe Royer
> Sent: September 18, 2006 12:59 PM
> To: veritas-bu at mailman.eng.auburn.edu
> Subject: [Veritas-bu] LTO3 minimums
>
>
> Forgive me if this has been asked before, I'm a bit behind on reading
> the list.
>
> How do you keep your LTO3 drives spinning fast enough?
It's an ongoing problem most folks are dealing with.
Multiplexing and disk staging (DSU, DSSU, VTL, etc)are the most common.
> I have a meeting with an idiot manager
Hehe. The is a public forum, eh? ;o)
> who refuses to believe that we
> can't stream fast enough to use LTO3 without damaging the tape and/or
> drive. I have limited DSSU space. I have been in
> environments in the
> past where shoeshining was normal and so was the 20% failure
> rate and I
> don't want to go back. It is my understanding that most
> people aren't
> spinning LTO3 fast enough and are living with higher failure rates.
To be honest, I haven't had many (any?) failures due to shoeshining with
the LTO2/LTO3 drives I have.
Just poor performance.
Now the DLT7000s I used previously were horrible for it.
With LTO Ultrium drives, the tape actually floats above the drive's
read/write head, so there's not nearly the destructive consequence of
shoeshing with older technology drives.
They just SUCK at writing less than "streamable" data rates.
You end up in a situation where the drive is shoeshining, (slow down,
stop, backup, spin up, find position, write, repeat) and then you end up
buffering writes on the media server, your buffers fill up, causing
delays, etc, etc.
>
> The only thing I can think of is to send everything to DSSU
> first (TSM
> anyone?), but NBU sucks at telling you the throughput there
> so I'm not
> sure I trust that anyway. Any tricks for getting throughput
> numbers out
> of NetBackup (5.1) DSSU duplicates are very welcome.
I don't really care ho long my dupes take, as they happen out of window,
as long as they get done.
I usually use iostat on the media server, if/when I'm concerned about
throughput to tape.
DSSU, and/or VTL are excellent options for getting the data in off the
clients and eliminating network/client performance from impeding the
ability to stream you drives.
Also, if you have some large high perf servers with lots of fast disk,
making those boxes SAN Media Servers can help.
Paul
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