topic Re: DDS Drive capacity in Operating System - HP-UX

DDS Drive capacity

Ram Kumar — Thu, 27 Jul 2000 22:14:22 GMT

WHat are the capacity of DDS-2/DDS-3 drive and also DLT4000/DLT7000 drives.

Please also mention the speed at which these drives can take backup of data

Re: DDS Drive capacity

Dan_4 — Thu, 27 Jul 2000 22:42:52 GMT

Product specs for the drives are available at:

http://www.hp.com/tape/mechs/mechprods.html

http://www.hp.com/tape/dltprods.html

Re: DDS Drive capacity

Manju Kampli — Thu, 27 Jul 2000 23:08:09 GMT

DDS2: 8 GB capacity and transfer rate of 3.6 GB/h with hardware data compression
DDS3: 24 GB capacity and transfer rate of 7.2 GB/h with hardware data compression*
DDS4: 40 GB* capacity and transfer rate of 21.6 GB/hour

DLT 4000: 20 GB native, typically 40 GB with hardware data compression. 1.5 MB/s (5.4 GB/h) native, typically 3 MB/s (10.8 GB/h) with hardware data compression

DLT 7000:40 GB native, 80 GB with hardware data compression. 6 MB/s (21.6 GB/h) native, up to 12 MB/s (43.2 GB/h) with hardware data compression

Re: DDS Drive capacity

Sundararajan Anandhan — Thu, 27 Jul 2000 23:45:49 GMT

Hi,

Parameter DDS2 DDS3

Native Capacity 4GB 12GB
Compressed 8GB 24GB

Speed
(Burst) 510KB/s 1MB/s
(non-compressed)
-----------------------------------------

Parameter DLT 4000 DLT 7000

Native Capacity 20 GB 35 GB
compressed 40 GB 70 GB

Speed 1.5MB/s 5.0MB/s

Hope This helps,
Regards,
Sundar

Re: DDS Drive capacity

Shannon Petry — Fri, 28 Jul 2000 10:54:59 GMT

The tape speeds mentioned all look good, but remember that those are manufactures MAXIMUMS, and not real life.
DDS2=8GB(Average 4-6GB)
DDS3=24GB(Average 18-20GB)
DDS4=40GB(Average 30-35GB)
DLT(4/7)000((HAVE NOT USED))
DLT8000=80GB(Average 65GB)
Thruput also is very dependant on how busy the system is. On a busy file server, your throughput is 1/2 a system that has a couple disks, and a single user running lite apps. Also depends on how many other devices are on the same bus. I.E. My DLT 8000 has great thruput, sitting on its own bus. I have many DLT4's which vary. One system has a disk array on the same bus, and is very slow to grab data from tape.
MFR Max is Okay for estimating, but system load is also critical to performance!
Best Regards,
Shannon

Re: DDS Drive capacity

Dave Wherry — Fri, 28 Jul 2000 14:32:07 GMT

Adding onto to Shannon's comments.
Shannon spoke of transfer rate and thru-put and is exactly right. It so much depends on system load and interface load. How many devices are there on a controller.
Shannon also put several numbers there, but, did not really talk about them. Those are capacity numbers and they are lower than the marketing specs. The maximum capacity is achieved in a controlled environment with near "perfect" data. By perfect I mean very little white space in files. Block sizes matching tape block sizes. Quality of the tape (new or older), how clean the tape head is affects compression ratios, etc...
In the real world you will be hard pressed to come close to the marketing capacity numbers. I've had a 4GB DDS that could not backup a 2GB file system on one tape.
The marketing numbers are a good place to start. Just do not expect to achieve them.