It's what's called the shoe-shine effect. It's where the drive has to stop
and start frequently because the data is coming into the drive too slow.
The drive has to frequently stop, rewind back some number of blocks, and
start again. It's not what I would call damage (since those operations
exist even under optimal conditions), but it's certain to cause excessive
wear, and will cause the drive and medium to fail more quickly.
This problem is not unique to SDLT technology, but because Quantum has
decided for engineering purposes to use only large buffers to address the
problem, it is more susceptible to it. Now, I'm not a hardware engineer,
but my impression is that buffering will help only intermittent
interruptions in the data flow. If the data rate is consistently slower
than the specified speed of the drive, it's going to have to stop anyway
(albeit less often).
Some LTO drives (HP for sure, and I think Seagate), will not only use
buffers to keep the data flowing, but also will attempt to somewhat
intelligently match the incoming data rate. You still have to be careful
there; with HP, it can only go down about 1/2 of its rated speed.
Quantum engineers tell me the reason they chose not to go with a variable
speed drive is because it reduces reliability of the drive in and of itself.
However, looking at Quantum's DLT product line, it seems to me that if they
have a customer who can't stream data at the rate demanded by SDLT, they can
offer them the VS80. LTO doesn't offer a solution whose data rate is such
that can be satisfied, for example, by FastE, so they had to use a variable
speed technology.
The best solution (always) is to acquire drive technology that is best
matched to the environment. Don't purchase or recommend the purchase of
drive technology based solely on media density...
--paul
----- Original Message -----
From: "Rehan, Savin" <savin.rehan AT HP DOT COM>
To: <NETWORKER AT LISTMAIL.TEMPLE DOT EDU>
Sent: Thursday, November 13, 2003 10:35 AM
Subject: [Networker] SDLT tapes and drives
Hi ,
We are new to SDLT technology and heard a rumour that if the backup
speed is below a certain level then it could damage the tape and/or
drive . Is this true ? Does anybody have any useful links on SDLT's
Savin
HP
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