DDS vs DLT tape drives

[Evgeny]

Hi all,

Can anyone tell me which is a superior format, DDS (3 or 4) or DLT 4? Specifically I'm comparing Quantum DLT 4000 to Sony SDT 9000. From the specs it seems like DLT is a little faster (1.5 vs 1.2 MB/s) and a little more reliable (1 bit in 10^17 uncorrected errors vs 1 bit in 10^15). Are there any downsides to it?

Evgeny

 

[Agamar]

The DLT may be a bit faster, but I personally prefer the DDS-4. Holds up to 40gig, and has a very small format.

 

[Peter]

The DDS format uses very fragile mechanical solutions, both in the tape and in the drive. After a short
adventure into this, we're back onto QIC's descendants - Travan until recently, with ADR now strongly
increasing.

The ADR drives are lots faster than either DDS or DLT, especially the SCSI versions, and error rate
is also better. Drives range from 30 GB IDE to 120 GB SCSI (all assuming 2:1 compression), with all
kinds of interfaces available, externals and internals. Native transfer rates are up to 4 MBytes/minute,
bit error rate 1 in 10^19.

The mechanical solution is the same as in QIC and Travan, practically no moving parts except for the
tape drive roller. Drives are surprisingly inexpensive, tape media pricing is reasonable considering that
they last much longer than DDS tapes.

http://www.onstreamdata.com

http://www.onstreamdata.com/products/index.html

regards, Peter

 

[Peter]

btw, the Quantum web site has the DLT4000 as a "retired product".

 

[Evgeny]

Agamar, don't both DDS-4 and DLT IV hold 20GB? I'm talking native capacity. 40GB is just a number some guy pulled out of his arse, they could just as easily say "200GB assuming 10:1 compression". Peter, I realise that it's "retired", I want to buy one second-hand and I have a choice between that one and a Sony DDS-3 drive. DDS-3 can only hold 12GB, of course, but the DLT one was significantly cheaper, so I started wondering if there's some good reason for that? So ADR is good, but my choice is between DLT and DDS.

 

[bozo1]

DLT IV is 35 or 40GB native - depending on the drive. DLT7000 drive is 35GB native, DLT8000 is 40GB native, both using DLTIV tapes. DLT4000 drives are 20GB native using DLTIV tapes. Old DLTIII drives were 10 or 15GB native using DLTIII tapes.

DLT 1 is a newer offering (why they went backwards with the number I don't know) and is 40GB native but runs at half the speed as DLTIV drives and is much cheaper.

SDLT is 110GB native and quite fast. We replaced our DLTIV drives with those at work last year. Tapes cost twice as much but store twice as much and are twice as fast as DLTIV drives.

 

[Evgeny]

Thanks, bozo1. But how does DLT IV compare to DDS (3 or 4)?

 

[bozo1]

DDS3 - 12GB native, 1MB/sec uncompressed transfer rate.
DDS4 - 20GB native, 3MB/sec uncompressed transfer rate.

DLT4000 - 20GB native, 1.5MB/sec uncompressed transfer rate.
DLT7000 - 35GB native, 5MB/sec uncompressed transfer rate.
DLT8000 - 40GB native, 6MB/sec uncompressed transfer rate.
DLT 1 - 40GB native, 3MB/sec uncompressed transfer rate.
SDLT - 110GB native, 11MB/sec uncompressed transfer rate.

 

[Peter]

just for the record ...

ADR - 15 or 25 GB at 1 to 2 MB/s (all native uncompressed), 1 error in 10^19
ADR2 - 30 or 60 GB at 2.5 to 4 MB/s (all native uncompressed), 1 error in 10^19
Drives are $250 to $1000 here in Germany (including software), tape media are
around $50 each.

Transfer rate variations are interface dependent - IDE, parport and USB models use the slower
unit, SCSI, FireWire and "fast IDE" models use the full speed one.

regards, Peter