Re: VTL - Fiber vs SAS

[DrFranken <midrange@xxxxxxxxxxxx>]

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

www.Frankeni.com
www.iDevCloud.com - Personal Development IBM i timeshare service.
www.iInTheCloud.com - 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.