e 1200-320 4g speed , brainstorming question

[mohannad]

hi guys,

theres no actual case this is only a brain storming question .

theres an issue that's been nagging me for a while now through out our implementation ive noticed that when installing the 1200-320 4g NSR on the MSL 6000 the maximum through put dosent exceed 3.2 GB/m which means about 60MB/s , this is not what i excpect this is a 4 GB interface connected to a 320 SCSI .

First, anybody had better results with this configuration in means of data transfer?

Secondly, what should be the speed constrain, i.e. bottle neck, on the whole data path, from the switch to the the NSR its 4 GB/s = 512 MB/s and on the SCSI its 320 MB/s ,are there any costrains on the SCSI speed ? should the internal device buses on the NSR itself be an issue to consider when calculating speed , actually i dont know whats the speed on these buses!!


i know this is a very lose end question but any idea anyone?

[Uwe Zessin]

How did you test it? Maybe your data source cannot deliver faster than 60MB/s.

There is a customer advisory which says:
""NOTE: The hot plug versions of the MSL5000 and 6000 causes the speed of the drives to be limited regardless of the interface used. The MSL5000 limits the drive speed to that of an Ultra 80 (80 MB/s) and the hot-plug versions of the MSL6000 limits the drive speed to that of an Ultra 160 (160 MB/s).""

http://h20000.www2.hp.com/bizsupport/TechSupport/Document.jsp?lang=en&cc=us&objectID=c01122518

I've tried some throughput tests with LT&T (Library and Tape Tools) on an MSL6000 with an LTO4 drive (no, I did not size it) and got the expected 160MB/s.

[mohannad]

hi Uwe,

actually the host is also has 4 GB interface , the note was good thanks , but also i dont remember if the tested enviroment had a hot plug device or not, but either ways i did achive the 160MB .

another question poped into my mind though,

whats the drive write speed doset affect the operation?

thanks

[Uwe Zessin]

Where did the data come from the throughput was 60MB/s?

Even a 4 GigaBit (bandwidth) interface on the host will not help if the true data source (e.g. a set of disk drives) cannot deliver, because they have to move their heads around to collect the data. Typical example is a file server with many small files.


> 4 GB/s = 512 MB/s

It is 400 MegaByte / second. The bit rate on the cable is 4.25 GigaBits, but every 8 data-bits are represented by 10 bits on the cable (8B10B encoding) and there is some protocol overhead.