Tape device & Glance question

[Ngoh Chean Siung]

Hi,

1) If I am using DDS2, DDS3 and DDS4 tape device to backup data (Let's take DDS2 tape as example), any different in term of speed, technology to backup data into tape and etc.

2) What is Glance Plus software for?

regards.

[A. Clay Stephenson]

The best performance in terms of speed and capacity will be DDS4, DDD2, and DDS2 in decreasing order of performance. Any of these can be used with the standard backup tools like tar, cpio, and fbackup. Fbackup is by far the best "free" choice as long as you are only interested in HP-UX to HP-UX backups and restores. Man fbackup/frecover for details. Fbackup's main advantage over tar and cpio is that is is multi-threaded and can have multiple disk reader processes feeding the tape drive simulataneously. It's also easier to access remote drive with fbackup. For more power, speed, and convenience consider the optional product Data Protector.

Glance is a component of HP's performance monitoring toolkit, MeasureWare. It gives a much more detailed analysis than traditional tools like sar provide. As an example, you can measure tape throughput by zeroing in a process's open files and note how fast the byte offset for the tape device changes.

[Ngoh Chean Siung]

Hi,

I try to use DDS4 and DDS2 tape drive to do file system backup (using fbackup). But, the time taken for these 2 devices is almost same. By right, DDS4 speed is faster than DDS2.

regards.

[Alastair Donaldson]

In order to get the full benefit of the DDS4 tape drives make sure that your tape cartridges are DDS4. If you are using DDS2 cartridges you may not see much speed improvement.

Also most of the DDS4 tape drives are Low Voltage Differential SCSI while the DDS2 and DDS3 tape drives are usually single ended. Make sure that your DDS4 tape drives are on an LVD bus. If you mix LVD and SE SCSI devices on the same bus the bus will operate at the slower speed.

[lawrenzo]

DDS4 tapes have should be able to hold more data, and also the i/o is improved from DDS2.

Glance plus is a monitoring tool for a system that displays stats for:

cpu utilization
disk utilization
top process'
memory report.

This is shown real time. There are other measureware tools available for historical information for a server.

[Ngoh Chean Siung]

Hi,

1) How to differentiate the LVD and SE SCSI? By command or physical look?

2) Can DDS2 tape device using LVD SCSI as well? Any impact?

3) Where I can get more info about DDS tape devices?

regards.

[Dexter Filmore]

Here is some information about DDS technology:

http://h20000.www2.hp.com/bizsupport/TechSupport/Document.jsp?objectID=lpg50457

Hope this helps

[Leif Halvarsson_2]

Hi,
Do a ioscan -fn and you will find some information about your SCSI adapters (as SE/LVD).

A DDS2 (SE) cad be connected to a LVD bus but, the bus (and all connected devices) will switch to SE mode and performance decrease.

Alco notice the differences in cable lenght between SE and LVD.