Matti Harvala wrote:
>
> Hello !
>
> I am looking for info of differencies between Quantums DLT 4700
> and Magstar 3590 High Performance Tape Subsystem Model B11.
>
> These two tape drives has approx. same capacity/GB in one unit
> but B11 is much more expensive. What are those things that makes B11
> worth of money in case of ADSM. I know that the technology is different
> but what those numbers really mean in practice...
>
> Does the ADSM access B11 diffrently than 4700, how does the tape indexing
> differ between B11 and DLT 4700, etc. etc.
>
> Best Regards,
> Matti Harvala
> Unix System Manager
>
> ===========================================================
> Matti Harvala * Phone: +358 (0)10 505 2254
> Nokia Mobile Phones * Fax: +358 (0)10 505 2899
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> ===========================================================
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.
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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