difference in speed of DLT8000 LVD AND HVD

[Ed Segura]

DLT-8000E-LVD DLT tape drive, 40-80GB, External, LVD

DLT-8000E-DIFFDLT tape drive, 40-80GB, external, HVD

[Vincent Farrugia · Accepted solution]

Hello,

The difference in speed between LVD and HVD DLT8000 is nothing whatsoever. Both have a speed of 6Mb/s natively. 12Mb/s compressed if you assume 2:1 compression.

HTH,
Vince

[Marino Meloni_1]

Hi Ed,

LVD and HVD are only electrical specification of the interface, (differents voltage level) that could encrease reliability vs distances.
No variation in the scsi protocol with his settings and specifications (speed and bus widly)
so just electrical incompatibility, that can overdue with a converter

marino

[Curtis Ballard]

The previous postings probably answered all your questions but I'll throw in my 2 cents.

As stated LVD and HVD refer to the type and level of the signals sent over the wire. There is also a second rating on LVD busses for the maximum transfer rate 80,160,320. LVD busses have a faster maximum rate than HVD busses but the real limiter in this case is the maximum transfer rate of the DLT drive. Since that rate is lower than the maximum HVD bus rate then the performance will be the same regardless of the bus type.

That satement may not be true for other tape drives. Any time the maximum burst rate of a drive is faster than the maximum rate of the bus you are using, there is a potential for a performance loss. In practice there very rarely ever is a performance loss unless the drive has a faster sustained transfer rate.

With SCSI busses in good condition you don't ever need to worry about too fast of a transfer rate either. SCSI busses negotiate for the proper transfer rate. If the HBA can run 160 and your drive can only run 10 then the drive will request 10 and the bus will run at that speed. Often we see recommendations to reduce the maximum transfer rate of the HBA via the Bios. That is never necessary unless there is a problem somewhere on the bus or one of the devices is negotiation speed incorrectly. If reducing the maximum rate gets the bus to work that's great but there is still a problem somewhere that might become an issue later.