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Extremely Slow Restore


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We have a brand new ADIC Scalar 24, LT03 system with fibre channel. When using it to archive to our Mac XServe, we get write speeds around 2400+MB/Min.

 

However, when doing a compare or a restore (or any other read function) it only achieves around 20MB/Min. The Scalar is capable of roughly the same read/write speeds, so something isn't working correctly. Restoring 1GB from Sony LTO3 tapes shouldn't take an hour or more.

 

We've swapped the LTO drive inside the Scalar, swapped fibre cables, bypassed the fibre switch, practically everything we can think of, we have swapped. The only thing left is the software.

 

Could there be something in Retrospect restricting the Scalar to such a slow read speed?

 

FYI:

OS X Server 10.4.3

Retrospect 6.1.126, driver 6.1.3.101

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Hi.

 

Restore has usually a slow start, since the tape drive spends more time locating the files spread across the tape(s) than actually reading. Towards the finish, where the files unique to that client is stored in sequence, the restore goes much faster.

 

What worries me is that you say that comparing is also slow. Is that the compare performed by the script immediately after the backup?

 

Regards

Lennart

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hi:

Sounds like a cool setup. I'd say 20MB/min means something hardware wise is mis-configured. I'd guess speed mismatch on the fibre line or something there. Is there a program from the tape drive manufacter that will let you test read/write speeds bypassing Retrospect? Do you have a windows system you could slap in there and try? My first guess would be something software/hardware wise with the fibre channel is wrong, to get such a mis-match speed.

Good luck.

-s

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Quote:

Hi.

 

Restore has usually a slow start, since the tape drive spends more time locating the files spread across the tape(s) than actually reading. Towards the finish, where the files unique to that client is stored in sequence, the restore goes much faster.

 

What worries me is that you say that comparing is also slow. Is that the compare performed by the script immediately after the backup?

 

Regards

Lennart

 


 

I would expect a slow start too, but it never speeds up. And I'm only backing up/restoring 1 6GB file, so it's not doing any searching. It should be a straight linear shot.

 

Yes the compare starts immediately. The compare speed is just as slow as the Restore speed = painfully slow.

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Quote:

I would expect a slow start too, but it never speeds up. And I'm only backing up/restoring 1 6GB file, so it's not doing any searching. It should be a straight linear shot.

 

Yes the compare starts immediately. The compare speed is just as slow as the Restore speed = painfully slow.

 


Then I'm stumped. Sorry. I have no idea.

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Quote:

 

hi:

Sounds like a cool setup. I'd say 20MB/min means something hardware wise is mis-configured. I'd guess speed mismatch on the fibre line or something there. Is there a program from the tape drive manufacter that will let you test read/write speeds bypassing Retrospect? Do you have a windows system you could slap in there and try? My first guess would be something software/hardware wise with the fibre channel is wrong, to get such a mis-match speed.

Good luck.

-s

 


 

It's a very cool setup grin.gif

 

Retrospect is my only application, no applications came with the drive. And no, no windows systems as we're all Mac here. All our other Fibre devices get 80MB/sec or higher.

 

We've swapped the LTO drive which contains the fibre connection, swapped fibre cables, bypassed the fibre switch, etc. The only thing ADIC and I can think of is that Retrospect itself is slowing down all the READ functions.

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Retrospect is published by EMC/Dantz Inc.

 

While there are some replies by Dantz employees to some questions, this is _not_ the official channel for technical support.

 

Tech support costs some money, but given the high value of the iron you're using, $75.00 doesn't seem like such a hardship.

 

There is undoubtedly a problem; Retrospect should be able to read files from devices without a slowdown.

 

Dave

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So I discovered this:

 

The Scalar was set for L Port topology (Arbitrated Loop). However, it is connected directly to the Mac only, so this should have been set to N Port topology (Point to Point).

 

When I change the Scalar to N Port, the Mac has no problems connecting to the device. I can verify this using Apple's Fibre Channel Utility and System Profiler.

 

The problem is Retrospect can not see the Scalar when it is set to N Port.

 

Questions:

1 - Why can't retrospect see the Scalar when set to N Port (Point to Point)? Retrospect states it supports Point to Point.

2 - Could my 100 times slower 'read' function have been a result of being set to the wrong topology?

 

Thanks.

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  • 1 year later...

I am having the exact same issue, a 2.3GB backup takes 4 minutes to write but requires over 2.5 hours to complete if the compare function is enabled. If I restore the data it takes even longer.

 

Don't expect to get assistance from EMC/Insignia/Dantz on this problem, a support technician confirmed they have a trouble ticket into Apple about fibre channel read latency, it has been a problem for some time now. Even with our Retrospect maintenance contract I was unable to find a resolution to the problem.

 

+ Executing Immediate Backup at 7/6/2007 10:30 AM

To backup set Restore Test…

 

- 7/6/2007 10:30:56 AM: Copying [filename] on Bank1…

7/6/2007 10:34:59 AM: Comparing [filename] on Bank1…

7/6/2007 1:08:14 PM: Execution completed successfully.

Completed: 19 files, 2.3 GB

Performance: 29.7 MB/minute (2372.7 copy, 14.9 compare)

Duration: 02:37:18 (00:03:05 idle/loading/preparing)

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