Discussions specific to tape backups
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paruccone
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media changer not recognized if connected through iSCSI

Post by paruccone » Apr 28, 2018 8:47 pm

Hi!

Using VBB I discovered than my adaptec controller has a driver limitation in its Win x64 version preventing to change the blocksize from its default. After realizing that Veeam doesn't run in 32bit versions of windows I tried Tape Redirector but now it is part of Virtual SAN and it's main service doesn't run... under windows 32bit (even though Tape Director itself did).

So I connected the controller to a Linux VM and exported it through iSCSI.

Both the tape and the media changer now appear under Windows management on the host in which I installed Veeam Backup but when I add a tape server (and after), only the tape is detected.

I tried to define the iSCSI targets both as separate LUNs within same target or as separate targets but neither worked.

Before anyone asks: I am using the same integrated windows driver as I did when the changer was recognized (if I use the manufacturer one Veeam doesn't recognize the media library even when not using iSCSI).

Thx!
Alex

Dima P.
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Re: media changer not recognized if connected through iSCSI

Post by Dima P. » Apr 29, 2018 8:00 pm

Hello Alex,

Is it possible to connect your library to a windows server? With Veeam B&R you can assign a tape server role to a remote windows host and connect tape device to that server.

paruccone
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Re: media changer not recognized if connected through iSCSI

Post by paruccone » Apr 30, 2018 7:55 am

Hi Dmitry,

as mentioned in the original post, that wouldn't help: Veeam requires x64, win x64 driver for my controller fixes blocksize at 64K -> bad transfer rate.

32bit driver for the SCSI controller works without the blocksize bug but Veeam doesn't run in 32bit environments.

I have found a 2nd hand LSI20320IE controller which should work much better than the Adaptec (and especially having a non-buggy x64 driver allowing up to 2MB blocksize) but my point here is really about how to troubleshoot VBB and understand why the autochanger is shown in device manager and not being detected because that would help me a lot in different scenarios.

Thanks,
Alex

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Re: media changer not recognized if connected through iSCSI

Post by Dima P. » Apr 30, 2018 1:33 pm

Alessandro,

What is the name of the tape device you are using?

paruccone
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Re: media changer not recognized if connected through iSCSI

Post by paruccone » Apr 30, 2018 1:53 pm

it's a Tandberg Storageloader LTO-4 connected via SCSI to an adaptec 20320LPE card and veeam correctly states that, most of time, the bottleneck is on the target (max 70MB/s). Of course already controlled the SCSI chain (termination, no other devices, etc.)

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Re: media changer not recognized if connected through iSCSI

Post by Dima P. » Apr 30, 2018 2:11 pm

paruccone wrote:adaptec 20320LPE card
Are you sure the model is correct? Cant find any specifications here.

paruccone
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Re: media changer not recognized if connected through iSCSI

Post by paruccone » Apr 30, 2018 3:01 pm

sorry, typo: https://storage.microsemi.com/en-us/sup ... -29320lpe/

2930lpe
problem: https://storage.microsemi.com/en-us/sup ... -29320lpe/

actually that's a design problem of the driver, not a limitation of Windows (documented by a guy who proposed to fix the code but the source has been lost when adaptec has been sold).

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Re: media changer not recognized if connected through iSCSI

Post by Dima P. » Apr 30, 2018 3:57 pm

Same links, but thanks. I actually see x64 driver for Windows 7/2008R2. Does it work?

paruccone
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Re: media changer not recognized if connected through iSCSI

Post by paruccone » Apr 30, 2018 4:50 pm

Dima, I never said that the controller is not working. The problem is that the controller's driver for win x64 forces block size to 64K impacting performance. This cannot be changed. Alternative would be to work in 32bit windows in order to avoid the faulty driver but veeam doesn't exist in 32bit version so the only work-around is connecting the tape/controller to something that is not using adaptec'cs faulty windows x64 driver.
Best option is iSCSI.
Now, can we get back to my question and: how can I troubleshoot why the changer not recognized? Maybe an iSCSI problem or not, but windows sees it correctly. As the tape is correctly recognized by both windows and VBB, I'd say the problem probably lies in VBB.

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Re: media changer not recognized if connected through iSCSI

Post by Dima P. » Apr 30, 2018 5:23 pm

Alessandro,

Thanks, was seeking for an option to use the proper driver as the setup with a man in a middle (i.e. linux host) is not supported: Veeam B&R requires a tape device to be directly connected to backup server or Veeam Tape Proxy component. Try to remove the changer driver via device manager and reboot this host. After that make sure that generic driver is installed. Once you see the changer and drives in the device manager try to rescan local tape server via Veeam B&R.

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Re: media changer not recognized if connected through iSCSI

Post by paruccone » Apr 30, 2018 9:53 pm

Thanks a lot Dima!

VBB is already working perfectly in the (I suppose) supported environment (Windows VM on ESX with passthrough SCSI controller + tape library).

That said, we're still talking of a small home setup (backup of personal data that I store in big quantities as a hobbyist photographer) so whether the solution is supported or not, it's not a real issue for me. But as a geek and +20 year IT professional, I was trying to hack my way around adaptec's faulty driver's limitations.

B plans being:

- the LSI 20320 controller I just bought for 15€ (its driver will allow me to set a block size up to 2MB)
- starwind's stand-alone tape director (if they are able to send me an old 32 bit version which existed but can't be found anywhere on the internet)
- correct iSCSI target setup in linux with TGT (looks like the tape drive is getting continuously disconnect so there more chances that the (wrong) iSCSI setup is causing VBB not to see the changer rather than VBB having a problem itself.

I will try to come back with my findings to share with the community ;)

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Re: media changer not recognized if connected through iSCSI

Post by paruccone » May 01, 2018 10:37 pm

Hi Dima!

Tried downgrading to esxi 5 which allows passthrough SCSI devices (vmware manages the controller, not the guest) and effectively I have plenty of choices showing up in VBB for block size. Problem is that the controller-emulation layer probably adds too much overhead and the trasfer rate is 10MB/s lower than with the PCI-passthrough controller.

Continuing my search I noticed that the tape server/service is 32 bit. Is there a way to install a 32bit tape-serve only role on a separate machine? In that case my problem would be solved.

Thanks!

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