Ultrium 960 LT&T Errors

[BR733612]

Hi,

I have setup this chain of drives as follows:

HBA Adaptec 19160LP -> Ultrium 960 -> Ultrium 215e -> VS80 -> Terminator

Now I seem to getting the highest speed reported by LTT is approx 14MB/s for write and 11MB/s for read! (5MB/s for VS80) I understand I dont have a Ultra 320 Card and cable to the Ultrium drive at present (this is planned in the future) but I should surely be getting higher speeds ??

The more to the point question is that when the VS80 is in line LT&T complains of a error it does a write test fine and then tries to read, then it requests a cleaning cartridge??

In the log its states something about 'Data Miscompararsion or something like that' and the read speed is reported at 33MB/s ???

Anyone know what I'm doing wrong as this is a real pain at present.

I know I wont get a full speed but would be nice not to get the error and maybe a bit faster ??

Thanks for any help

Ed

[Lewis Finch]

Ed, Having these devices daisy chained is a bad idea. You will never get any kind of performance out of the Ultrium this way. Put it on it's own controller. Here is some further info for you.

http://h20000.www2.hp.com/bizsupport/TechSupport/Document.jsp?objectID=lpg50460

[BR733612]

Hiya,

This I understand however - even with the terminator on the end and Ultrium 960 on its own I still get the above results (No read erros mind you) Is that what you would expect from that performance ??

It seems odd - Unfortantly I dont have a second channel or port, but still don't understand why this should be happening? I understnad perfoamnce will be poor but this poor ?? and errors?? they are all LVD drives from what I understand ?

Thanks

Ed

[Lewis Finch]

Ed, if you read the document I gave you, it will help performance tune the Ultrium tape drive. Also in that doc is a link to the Library and tape tools diagnostic that will allow you test your system performance. Just because they are all LVD drives does mean they will all perform the same. Having a VS80 daisy chained to an Ultrium will severly limit it's performance

[BR733612]

Hiya,

Okay thanks for that - have read all. Now intreastingly I have run a Tape Performance test. If I use test parameters Varible and Fixed I/O Size at 64k and 128k and dont read the tape I get 71MB/s. No Compression 74MB/s, 2:1 71MB/s, 3:1 66MB/s. Yet when I read the tape as part of the test the I/O fails ???

Am I misssing something why work one way and fail the other ?

The read failure doesnt occur when the VS80 is removed. I understnad the VS80 will cause performance issues however if its writing at 71MB/s why fail on the read ?

So if my maths is corret its about 252GB/hr which on a Ultra 160 card should be right ?? or am I talking nuts.

When I do a Read/Write test with the Test for the device I only get 17MB/s ??

Thanks

Ed

[Curtis Ballard]

Ed,

You are correct that while an Ultra 320 card is recommended the drive can maintain streaming with most data sets while using a 160 card as long as the system can handle that I/O speed. Some compressible data will require more than 160 to get full performance so the 320 card is recommended.

For the read errors when the VS drive is attached I suspect that you are running into signal degradation caused by loading of the VS drive, additional cabling, or the connectors. Ultra 160 signals are very succeptible to degradation caused by capacitive loading in the cables and connections are bad. Just a little rounding of the signal transition and you lose a bit or a control signal.

Reading and Writing will be different because of which end is driving the signals. During writing the HBA is driving the data and the drive only controls the ACK signals. During reading the drive is driving the data. The drive and HBA likely have different transceivers with different transition characteristics so the bus loading will have different effects.

These kinds of speeds and multiple devices on the bus just don't mix well.