Creating zones or vlans is easily done on any modern managed switch (FC
or Ethernet).

A concern I have, is the IO bus of the system you are using. Even the
PCI-e bus has bandwidth limits, and depending how the system is
designed, even a single port HBA may have to share bandwidth with
adjacent slots.

With some detail as to the environment, you could probably get better
help.

What system is your media server?

What vendor do you use for your SAN?

Are you writing D2T or D2D2T?



-----Original Message-----
From: veritas-bu-bounces AT mailman.eng.auburn DOT edu
[mailto:veritas-bu-bounces AT mailman.eng.auburn DOT edu] On Behalf Of David
Magda
Sent: Wednesday, July 27, 2011 5:15 PM
To: Len Boyle
Cc: Veritas-bu AT mailman.eng.auburn DOT edu
Subject: Re: [Veritas-bu] multipathing with tapes on Linux?

On Wed, July 27, 2011 17:03, Len Boyle wrote:
> David,
>
> I think the answer depends on what you mean by multi-pathing, and the
> maker of the tape drive.
>
> The new IBM tape drives include two ports. But I think that it is only
for
> failover. And I suspect that the support would only be in the IBM tape
> driver. Which  was released with it's source code the last I looked.
>
> I also suspect that you do not need multi-pathing to feed the tape
drives.
>  The  native speed for  a lto-5 tape drive is greater than that of a
gige
> card. And if you send data that can be compressed 2-1 or 3-1 then
even
> more so.
>
> The hard part is getting the data off the disk fast enough to drive
the
> tape drive.

We have sixteen LTO-4 drives that we want to drive with as few media
servers as possible for support reasons. If we could get a few servers
with 10 GigE and and multiple HBAs (or a single multiport HBA), then we
could (attempt) saturating the 10 GigE and having 8 or 12 Gbps of FC on
the other end going to multiple drives in a library.

If multi-pathing is not supported, another option would be to configure
FC
zone such that: drives 0-3 are only visible to HBA0-port0, drives 4-7
visible to HBA0-port1, drives 8-11 visible to HBA1-port0, and drives
12-15
visible to HBA1-port1.

We'd prefer to have "normal" multi-pathing if possible, but spreading
the
tapes to different HBA ports is another possibility.

We're not concerned with multi-pathing on the drives, but utilizing as
much bandwidth from the clients to the media server, and from the media
server to the library/drives.

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