Tape Redirector very slow?

Tape drive and auto-loader redirector over iSCSI

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Futureweb
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Mon Oct 27, 2014 9:07 am

Hello,

following configuration given:

Server 1: HP DL380G8, Dual Octa-Core-Xeon, 128GB RAM, 10 Samsung Server SSDs, HP Tape-Library (SAS) running Windows Server 2012 R2
Server 2: ICO Server, Dual Hexa-Core-Xeon, 64GB RAM, Multiple HDD RAIDs running Windows Server 2012 R2

Those 2 Servers are connected through HP ProCurve 3400cl-48G Switch.

The Problem: We have MS DPM running on Server 2 - iSCSI connected to HP Tape Library on Server 1 - Network-Saturation never goes over 40%.
With Jumbo-Frames deactivated we get 40-45MB/s - with enabled Jumbo-Frames we get about 45-50MB/s. (less Overhead = more MBs/ with same Network Saturation)
On Initiator Side we hat to set "[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4D36E97B-E325-11CE-BFC1-08002BE10318}\{...}\Parameters]" - MaxTransferLength DWORD = 0x10000 (was 40000) to get Tape-Library running without Problems.
We also tried Starwind iSCSI-Initiator - but with this one it didn't work at all.

With direct attached Tape-Library we get over 100MB/s ... but with the 40-50MB/s we get now we can't Backup efficiently as the Backups start so stack up .... (30-40 Hour for backing up everything ... no daily Backups possible)

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(Ports 5-6 is the connection between those 2 Servers - it's almost everytime at ~40% usage)

Is there any sort of Bandwith-Limitation on the Tape Redirector? Or does anyone have an Idea how to get the Speed up?

Thank you, bye from Austria
Andreas Schnederle-Wagner
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anton (staff)
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Mon Oct 27, 2014 4:55 pm

There's no built-in limitation or synthetic bandwidth throttling, rather it's a "pure synchronous" model for SPTI requests Microsoft has (one of the reasons we don't allow now redirecting hard disks the same way we do with tapes as performance sucks badly). You may try to:

a) Throw in more physical Ethernet connections / iSCSI MPIO paths. This *may* work.

b) Use Virtual Tape Library and go Disk-to-Disk-to-Tape instead of a Disk-to-Tape scenario. This is going to work for sure as it's a production scenario we recommend and actively push.

Good luck :)
Regards,
Anton Kolomyeytsev

Chief Technology Officer & Chief Architect, StarWind Software

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Futureweb
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Tue Oct 28, 2014 9:11 am

Hello Anton,
do you think upgrading to 10GBit would help with this Speed Issue?
I'm not sure about this - as some other People wrote in the Boards that it did NOT help them speeding up the iSCSI Tape Redirector ...

D2D2T would be nice but not very practicable with our Scenario. (*Hosting Servers - Datacenter* --> *ICO Backup Server - local - MS DPM* --> *HP Server - local*)
In first Place we had the Tape Library directly attached to the ICO Server (where we got our Disk Backups already) ... but as it had some issues with the stability so we moved the HP Tape Library to the HP Server ... (Stability issues gone - but Speed issues now)
So we already got our Disk Backups on ICO Server ... would be a bit "weird" to have them double ... :)

Andreas
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anton (staff)
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Tue Oct 28, 2014 9:16 am

1) It depends on how device processes the commands. If it does allow "overlapping" of them (has per-tape queue) it will (just like throwing more Ethernet connections). If no - there's not much we can do unfortunately.

2) Take a look @ our VTL just to make sure it's not what will help:

http://www.starwindsoftware.com/vtl-page
Futureweb wrote:Hello Anton,
do you think upgrading to 10GBit would help with this Speed Issue?
I'm not sure about this - as some other People wrote in the Boards that it did NOT help them speeding up the iSCSI Tape Redirector ...

D2D2T would be nice but not very practicable with our Scenario. (*Hosting Servers - Datacenter* --> *ICO Backup Server - local - MS DPM* --> *HP Server - local*)
In first Place we had the Tape Library directly attached to the ICO Server (where we got our Disk Backups already) ... but as it had some issues with the stability so we moved the HP Tape Library to the HP Server ... (Stability issues gone - but Speed issues now)
So we already got our Disk Backups on ICO Server ... would be a bit "weird" to have them double ... :)

Andreas
Regards,
Anton Kolomyeytsev

Chief Technology Officer & Chief Architect, StarWind Software

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Futureweb
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Joined: Mon Oct 27, 2014 8:52 am

Tue Oct 28, 2014 9:25 am

1) could you explain a bit more what you mean with the "overlapping" / "per-tape-queue" - I'm not really sure what this means
2) already had a look - I like the concept - but it's not fitting our scenario as we already got the Disk Backups - (in our old Scenario - where the Tape Library was connected directly to the ICO Server - it was a D2D2T-Solution - but we had to move the Library to the HP Server because of stability issues with ICO Server and HP Library ... so the problem is now: How to get the Disk Backups (stored on ICO Server) to Tape (connected to HP Server) within an acceptable time)

Andreas
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anton (staff)
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Tue Oct 28, 2014 9:32 am

Feature of a tape drive to accept WRITE commands and confirming them w/o actually putting data on tape. Disk drives do this all the time.
Futureweb wrote:1) could you explain a bit more what you mean with the "overlapping" / "per-tape-queue" - I'm not really sure what this means
2) already had a look - I like the concept - but it's not fitting our scenario as we already got the Disk Backups - (in our old Scenario - where the Tape Library was connected directly to the ICO Server - it was a D2D2T-Solution - but we had to move the Library to the HP Server because of stability issues with ICO Server and HP Library ... so the problem is now: How to get the Disk Backups (stored on ICO Server) to Tape (connected to HP Server) within an acceptable time)

Andreas
Regards,
Anton Kolomyeytsev

Chief Technology Officer & Chief Architect, StarWind Software

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Futureweb
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Tue Oct 28, 2014 9:37 am

alright - do you maybe know if the HP MSL2048 with LTO-5 Ultrium 3000 Sas Drive can do this? (Google was not very helpful on this)

as for "a) Throw in more physical Ethernet connections / iSCSI MPIO paths. This *may* work." - how should/could this help? This is 1 Connection/Session - so only 1 Path would be used - or do I miss something?
Futureweb
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Wed Nov 05, 2014 1:31 pm

alright - even with 10GBit we can't get near our Speed we get with direct attached Tape Library - so we have to drop the Tape Redirector and go back to direct Connection ... sad ... as this would have been a really cool Solution if the speed would be ok! :-/
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anton (staff)
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Wed Nov 05, 2014 4:33 pm

There's not much we can do unfortunately except Disk-to-Tape --> Disk-to-Disk-to-Tape scenario.
Regards,
Anton Kolomyeytsev

Chief Technology Officer & Chief Architect, StarWind Software

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