It Depends. :-)

First we don't know if you have 8 internal disks, 18 internal disks, or 42 internal disks. We don't know if they are 10K spinny disks, 15K Spinny disks or SSDs.

We don't know how many processors you have or how much memory you have. We don't know how much data you have.

We don't know if you have 5 ginourmous Db2 tables eating 80% of your disk or if you have 25 million objects in the IFS using up that storage.

We also don't know if the Cybernetics unit is the very smallest with only 4 drives or a 4U behemoth with 36 drives in there.

All these things matter when determining how much throughput you need and your system is capable of generating.

HOWEVER the rule of thumb is that for a single partition system a SAS connection will do just fine and will do so a fair bit cheaper than will a fiber attached one.

And the short answer is your DASD is almost ALWAYS the bottleneck even when it's done very very well. :-)

- Larry "DrFranken" Bolhuis - Personal Development IBM i timeshare service. - Commercial IBM i Cloud Hosting.

On 1/29/2020 1:31 PM, Kevin Monceaux wrote:
Midrange Fans,

I'm reviewing quotes for VTLs. I currently have one from Cybernetics and
one from LaserVault. One quoted for SAS, the other for fiber. Our current
TS3100 physical tape library is connected via 57B3 3GB SAS cards. Our
internal DASD is connected to two 57D8 8GB SAS RAID controllers.
Unfortunately when our business partner initially set up this box they
optimized the RAID array for size instead of for performance, so all DASD
I/O is going through one RAID controller, and the other will only take over
if the active controller fails. With that in mind, would there be any
benefit from connecting a VTL via fiber, or would our internal DASD be a
bottleneck? All of the above pertains to an 8286-41A.

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