[rescue] Sun 20/40G 8mm tape drive (Exabyte 8900) - blocking factor / throughput ?

[Peter Stokes]

Hi

Not sure which version of tar you are using, but if you have the blocking factor option ‘b’ then try different values of that to improve the throughput. The density options were for the 9 track tapes from memory, so not sure if relevant here. I do remember the Exabytes were not that fast (though the 8900 was an improvement over the 8500) and the SS10 only has narrow SCSI for disks internally. You should get the best performance using an SBus controller and you need to keep them spooled up, ie need to keep them fed with data, otherwise you get the old shoeshine problem.

Sorry not a lot of help, it was a very long time ago since I played with them……

Peter

Sent from my iPad

> On 20 Dec 2023, at 01:47, vom513 via rescue <rescue at sunhelp.org> wrote:
> 
> Hello all,
> 
> Playing around with one of these connected to an SS20 running Solaris 9.  I added it correctly to st.conf based on Sun’s docs.  I’ve tested it on both the onboard 50pin esp bus as well as an SBUS Qlogic ISP card.
> 
> I’m seeing the same behavior as the second message in this thread:
> 
> http://www.linuxmisc.com/3-solaris/f04decafd0af71a2.htm
> 
> By default, I get ~ 1.3 MB/s (I’m just tar’ing up /usr - ~ 900 MB).
> 
> Here is one of my tar commands:
> 
> time tar cpfb /dev/rmt/1cn 480 -C /usr/ .
> 
> Ive tried the blocking factor mentioned (which my math puts at 480).  I don’t seem to see any difference / improvement - speed is still the same.
> 
> I’ve also tried the ‘h’ and ‘u’ density rmt devices with no change.  I’ve tried ‘c’ and no ‘c’ as well.
> 
> Does anyone know if there is something else I may be missing or otherwise how to get this thing to get close to it’s rated speed ( ~ 3MB/sec - so double what I’m getting).
> 
> Thanks.
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