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LTO-4 direct fibre blows away LTO-4 through an NSR...

Tom O'Toole
Respected Contributor

LTO-4 direct fibre blows away LTO-4 through an NSR...


I have posted before about my difficulty getting past 135MB/S with LTO-4 on MSl6000 libraries with e1200-320-4GB NSR. I just tested an MSL4048 with direct fibre to the drives using openVMS and immediately got 225MB/S, and that's with encryption. So, there ya go, the NSR IS the problem.
Can you imagine if we used PCs to manage our enterprise systems? ... oops.
7 REPLIES
Steven Clementi
Honored Contributor

Re: LTO-4 direct fibre blows away LTO-4 through an NSR...

Yes, of course it is. When you put a resistor into a serial circuit... what happens? ;o)

It is not so much a problem as it is a design flaw perhaps. Afterall, it is a SCSI - to - Fibre bridge... there has to be some drop in performance as compared to native fibre devices.

The real question is...

How much of a performance gain did you get when you upgraded from a standalone SCSI Tape Drive/Library that was utilized on a single machine to back up clients across the network... to a SCSI based Library with a Fibre Bridge? Was that gain as big as 90MB/s? or Bigger...


Steven
Steven Clementi
HP Master ASE, Storage and Clustering
MCSE (NT 4.0, W2K, W2K3)
VCP (ESX2, Vi3, vSphere4, vSphere5)
RHCE
NPP3 (Nutanix Platform Professional)
Uwe Zessin
Honored Contributor

Re: LTO-4 direct fibre blows away LTO-4 through an NSR...

I think the primary limitation is in the MSL:
""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***).""

c01122518 - ADVISORY (REVISED): HP StorageWorks MSL5000/6000 Interface Controller/Fibre Router Does Not Have Enough Bandwidth for Two HP StorageWorks LTO-4 Ultrium 1840 Tape Drives

http://h20000.www2.hp.com/bizsupport/TechSupport/Document.jsp?lang=en&cc=us&objectID=c01122518
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Tom O'Toole
Respected Contributor

Re: LTO-4 direct fibre blows away LTO-4 through an NSR...


I'm not sure "of course" covers it.

It has been difficult for me to get hard info from HP and I've spent a fair amount of time testing and isolating this, coming to the above conclusion, but unable to prove it. Search for my previous posts in this forum. I've also opened cases with HP in both VMS and storage without conclusion. The only doc HP has about the NSR's internal limitations are the quickspecs for the standalone (n1200-320 4g) device, specifying a 230MB/S internal bandwidth, and the well known advisory about two lto-4 drives on an NSR.

The advisory is not very useful, mostly because it contains no actual performance data. The fact is, the NSR can't drive a single LTO-4, let alone two. The 135MB/S single stream perf. is significantly below 230MB/S.

There is no SCSI speed limitation in this case, as I don't have hot swap drives, the scsi bus speed is reported by the NSR to be 320.

Can you imagine if we used PCs to manage our enterprise systems? ... oops.
Uwe Zessin
Honored Contributor

Re: LTO-4 direct fibre blows away LTO-4 through an NSR...

Ah, sorry. I somehow thought you had a hot-plug library and didn't know this limitation.
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Marino Meloni_1
Honored Contributor

Re: LTO-4 direct fibre blows away LTO-4 through an NSR...

Tom
I do not know if you have a MSL600 wich was hotswapp and you are using drive that are non hotswapp, or if you are using the new model that do not have onboard the hotwsapp card.

in case you are using the first one, even if your drives are attached dirctly to the nsr, you will have the the same limitation already listed in the previous post (160)

if you have the new model, this limitation do not exist as there is no other devices on the internaly that can slow down the communication.

In that case, you may have problem with the NSR that may have to handle huge amount of unsollicited SCSI commands sent over the SAN, you may have a look at the traces in order to identify this situation

marino
Tom O'Toole
Respected Contributor

Re: LTO-4 direct fibre blows away LTO-4 through an NSR...


Thanks - I think it is all non-hotswap stuff, but I'll check that out. All these little secret gotchas with the MSL6000 are annoying, I gotta say. Wonder how many customers are getting suboptimal performance and don't even know it?

I guess we'll soon learn all the annoying secret gotchas of the G3 series:-)
Can you imagine if we used PCs to manage our enterprise systems? ... oops.
Marino Meloni_1
Honored Contributor

Re: LTO-4 direct fibre blows away LTO-4 through an NSR...

For your reference:


http://h10010.www1.hp.com/wwpc/us/en/en/WF04a/12169-304612-304622-304622-304622.html

13.8 TB/hr >> 138000 Mb/hr X 16 drives
13800 / 16 = 862.5 TB/hr X 1 drive
862.5 / 3600 = 240 MB/Min
240 / 2= 120 MB/min Native


If you look at the quick speck it is indicated that LTO4 in a MLS5xxx or MSL6xxx will have limited transfer rate

http://h18006.www1.hp.com/products/quickspecs/11863_div/11863_div.html

Tape Drives HP MSL6000 LTO-4 Ultrium 1840 Tape Drive
NOTE: For use in the MSL5000 Ultrium libraries; data transfer rates up to 80 MB/s.
NOTE: For use in the MSL6000 Ultrium libraries; data transfer rates up to 160 MB/s. AJ028A
HP MSL6000 LTO-3 Ultrium 960 Drive
NOTE: For use in the MSL5000 Ultrium libraries; data transfer rates up to 80 MB/s.
NOTE: For use in the MSL6000 Ultrium libraries; data transfer rates up to 160 MB/s. AD612B