> Hello,
>
> From a tape device perspective, the following are key differences:
>
> DLT-4000
> I/O Throughput: 1.5 MB per second native
> 1.5 * compression rate (typically 2.25 MB per second)
> Capacity: 20 GB (native) or 20GB * compression factor (40 GB+)
>
> 3590
> I/O Throughput: 9.0 MB per second native
> 9.0 * compression rate
> Capacity: 10 GB (native) or 10GB * compression factor (20 GB +)
>
> Items to consider:
>
> 1) 3590 is extremely fast,; however, your backup software must support
> I/O multiplexing to achieve device capable speeds. Without
> multiplexing, I/O will be constrained by the DASD transfer rate. It is
> almost impossible to keep a 3590 tape device busy with one I/O stream.
> (ADSM does not support multiplexed I/O). To achieve desired performance
> under the current architecture it is better to have multiple slower
> drives working in parallel.
So IBM's sw is not utilizing IBM's best tape drive fully... ? :0
You are not IBM guy I think, from e-mail address, but you seems to know things
very well...Do you have any idea if it is planned by IBM to get ADSM support
multiplexed I/O ???
> 2) On SCSI F/W with two drives per controller, it will be hard to
> achieve 18 MB per second (One 3590 controller and two tape transports).
> I have performed some testing with other high-end tape devices and was
> only able to achieve 14 MB per second with two drives on one SCSI bus
> with two tape controllers. I suspect the use of one controller with two
> drives on one bus will achieve far less than 18 MB per second. Coupled
> with ADSM's lack of multiplexing technology, your probably looking at
> less than 4.5 MB per second per drive (guess).
>
> 3) It boils down to cost - are you willing to pay for something that you
> may not be able to fully use or exploit.
>
> 4) A new version of DLT will be released at year-end (DLT-7000). It is
> similar to DLT-4000 except native performance is 5.0 MB per second or
> 5.0 * compression factor. Additionally, capacity has been increased to
> 35 GB native/70 GB compressed. I suspect the price/performance point
> for DLT-7000 will be favorable versus other technologies.
>
> 5) I do not know pricing for 3590, but DLT is relatively inexpensive.
>
> 6) Media search time is also important. With larger media capacity
> substantially more data is store on one physical cartridge. You may
> want to compare the average access times for each technology.
>
> 7) Disaster recovery - does your DR site support either technology.
> DLT-4000 has been around for a while and is readily available. I am not
> sure about 3590.
>
>
> I hope I have given you something to consider....
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