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smd32
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Repository with DD Boost, concurrent tasks

Post by smd32 » Jan 12, 2017 10:29 pm

We are evaluating Data Domain Virtual Edition, and after setting up a few DD Boost storage units on the VM, Veeam always winds up setting the maximum concurrent tasks for each repository to 45. This is a lot higher than the usual 4 or 8 we use for standard storage devices.

Is this 45 task limit reasonable in general for DD Boost, and reasonable when using multiple storage units on the same DD appliance? We went with multiple storage units so we can get better visibility into dedupe ratios and disk space usage. My hunch is that we should have 45 tasks for the entire appliance and divide (not necessarily evenly) this among the number of storage units -- but the starting point of 45 itself seems a little weird.

FWIW on a per-job basis, we are using incrementals with weekly active fulls, Optimal compression, and Local target 16TB+ or storage optimization.

Thanks!

foggy
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Re: Repository with DD Boost, concurrent tasks

Post by foggy » Jan 13, 2017 12:14 pm

Hi Scott, this comes down to the max number of streams supported by the storage, which is 90 in your case (the number of tasks is set to 50% of that, taking into account other possible activities: restore tasks, storage replication, etc.). In case of multiple storage units it is indeed reasonable to divide that number evenly between repositories - you can either configure each of them explicitly or limit the max number of streams for each unit on the storage side, in this case Veeam B&R will set 50% of that number for corresponding repository.

smd32
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Re: Repository with DD Boost, concurrent tasks

Post by smd32 » Jan 13, 2017 3:51 pm

Thanks, Alexander. And in the Veeam 8 notes about DD Boost, it says that backup jobs using DD Boost are single-threaded. In 9.5, I can see multiple VMs getting backed up at a time going to a DD Boost repository. So has this process now become multi-threaded, or is there something else (the DD Boost server-side work?) that still is single-threaded in 9.5?

foggy
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Re: Repository with DD Boost, concurrent tasks

Post by foggy » Mar 21, 2017 12:32 pm

Sorry, Scott, missed that thread for some reason. Provided per-VM chains are enabled, Veeam B&R uses multiple write threads within a single job pointed to Data Domain. Without per-VM option, disks/VMs are processed in parallel, but data is written into a single file, so single write thread is used.

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