Re: VTL - Fiber vs SAS

[DrFranken <midrange@xxxxxxxxxxxx>]

You are correct that 4 LTO6 drives all in all out max compressed 
throughput is roughly 13Gb per second. This is 2/3rs more than a single 
8G port can support.

However it would be quite rare for most IBM i customers to have a 
sufficiently sized system to drive those drives to that level!!

That said, if you've invested in four drives you likely have a pretty 
big system and should do your homework on port speed, and for that 
matter the PCI-e Slot speed you're using!!

For THE VAST Majority of IBM i customers upgrading their tape drive 
beyond LTO6 is likely to result in zero reduction in backup time. Most 
wouldn't notice anything above LTO5. They just don't have the I/O 
infrastructure to push it.

Only reason I bring this up is I hate to see customers investing in LTO7 
drives (And $50+ Tapes) along with 16Gb Fiber ports when a SAS card with 
LTO5 drive (And $20 tapes) will do the backup in the same time!

        - Larry "DrFranken" Bolhuis

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

On 1/30/2020 8:10 AM, Holger Scherer wrote:
> right. Then also not to forget to have the IBM i host have multiple NPIV capable ports to gain faster speed.
> It's of not much use to have one 8GBit fiber port on the host and 4 fast LTO6 drives with one 8GBit (or faster)
> port for each drive. Been there, done that ;-)
> -h
>
> > Am 30.01.2020 um 13:59 schrieb Rob Berendt <rob@xxxxxxxxx>:
> >
> > One big difference between a VTL and one of those IBM 3xxx series physical libraries with multiple drives is that the VTL uses a single port on the NPIV capable switch even if it has multiple tape drives configured in it.  The physical library has you run a separate cable from each drive in the library to the NPIV switch.
>