In regard to: Re: [Networker] licensing requirements for driving library's...:

Actually, that isn't quite accurate. Even under Solaris 9, if you tune
the gigabit ethernet card and TCP/IP as well as use a separate VLAN with
jumbo frame support, you can drive signficantly higher throughput. We
use a Sun V490 and and keep 6 x LTO-2 drives spinning at max.

I'm not sure I understand.  Are we on the same page, that a gigabit
ethernet interface means an interface with a maximum transfer rate of
1 Gigabit per second, and that converting that to bytes means
a maximum transfer rate of approximately 125 Megabytes/s?

If we agree on that much, then we agree that the absolute maximum amount
of data anyone can push through a single Gigabit ethernet interface, per
second, is approximately 125 MB.  That's assuming no overhead whatsoever.

Searching on the net, I see that the maximum transfer speed of an LTO-2
drive in *uncompressed* mode is 30 Megabytes/s.  That's *without*
compression.  Is that figure incorrect?

Assuming that figure is correct, your assertion of pushing 6 drives at
maximum throughput (assuming uncompressed mode) amounts to

        6 drives * 30 Megabytes/s = 180 MB/s

One of us is clearly incorrect -- if it's me, I would be thankful if
someone would point out where my misunderstanding is.

Tim

--
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-----Original Message-----
From: Legato NetWorker discussion [mailto:NETWORKER AT LISTSERV.TEMPLE DOT EDU]
On Behalf Of Tim Mooney
Sent: Monday, December 12, 2005 4:42 PM
To: NETWORKER AT LISTSERV.TEMPLE DOT EDU
Subject: Re: [Networker] licensing requirements for driving library's
drives with > 1 server

In regard to: [Networker] licensing requirements for driving
library's...:

It seems to me that in order to accomplish this I can
(a) get a low-end Sun box capable of driving 6 LTO3 drives over fiber

(i.e.

maybe a 440), or
(b) continue to use the SF280s I'm using now, each driving two LTO3

drives.

I'm uncertain what sort of licensing requirements there would be, were

I to go with option (b).

For a couple of reasons I won't get in to here, I do not plan to back
up data in a SAN (i.e. backup traffic will traverse our gigE switched
network
instead.)

How many GigE interfaces are there on your server(s)?

With a theoretical maximum of ~ 125 MB/s and an actual maximum much
lower than that, you may not be able to push even one LTO3 drive over a
single gigE link.  I'm not sure if Solaris 10 is supported yet as a
backup server (we use Red Hat Linux), but graphs I've seen indicate that
the new TCP/IP stack in 10 does indeed improve performance
significantly.

If you only have one gigE link coming into the server, you'll need to
consider backup to disk, possibly followed by staging to tape.

BTW, I was at LISA '05 last week, and went to a number of the
backup-related BoFs.  Curtis Preston hosted a few of them, and he really
stressed the point that a single gigE link just won't do it for even the
previous generation of tape drives.

Tim

--
Tim Mooney                              mooney AT dogbert.cc.ndsu.NoDak DOT edu
Information Technology Services         (701) 231-1076 (Voice)
Room 242-J6, IACC Building              (701) 231-8541 (Fax)
North Dakota State University, Fargo, ND 58105-5164

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