> On Mar 11, 2016, at 6:56 PM, Alan Brown <ajb2 AT mssl.ucl.ac DOT uk> wrote:
> 
> On 11/03/16 20:14, Simon Templar wrote:
>> In my case using spooling didn’t prevent shoe-shining; it just introduced 
>> long pauses while data was spooled. I think all this means is that I can 
>> read from my data sources faster than my tape can write.
> 
> Unless you are using DAT, do not use mechanical drives for spooling - they 
> can't keep up with the tape drive unless you're using one that's dedicated 
> and only spooling/despooling for a single job (LTO1-2-3, incompressible data) 
> or can't keep up at all (As above with any form of compressible data, or 
> LTO4,5,6,7)
> 
> SSD is the only way to fly. After having tested with a PCIe NVMe drive, I'd 
> say that's preferred, but a _fast_ SATA2/3 or SAS2 drive will work too (The 
> old spool was a stripe of Intel SLC SSDs, the new one is a DC3700 card)
> 
> Spooling really comes into its own when you're running multiple jobs. Whilst 
> one job is despooling, others can be spooling. The interleaving effect means 
> all your jobs complete in a faster period of time.

Perhaps I should start testing with multiple concurrent copy-disk-to-tape jobs.

> As well as increasing max file size you need to boost the tape buffer size 
> from the 64kB default. I use 2MB

This is a hardware setting?

I tried Minimum block size & Maximum block size on my tape drive, but need to 
try it again.

--
Dan Langille - BSDCan / PGCon
dan AT langille DOT org

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