Veritas-bu

[Veritas-bu] Ethernet Bottleneck - need design suggestions

2002-12-18 16:54:05
Subject: [Veritas-bu] Ethernet Bottleneck - need design suggestions
From: veritas-bu AT jasons DOT us (veritas-bu AT jasons DOT us)
Date: Wed, 18 Dec 2002 16:54:05 -0500 (EST)

On Tue, 17 Dec 2002, Chip Paswater wrote:

> Hey folks,
>
> I'm having some bottleneck issues with my backup design.  Here's the
> scenerio:
>
> 1 Sun E4000 with 8CPU 8GB and single gigabit ethernet
> ADIC Scalar 1000 Tape Library with 8 LTO drives
> LTO Drives are capable of 15MB/sec
> Sun and TL are both connected to SAN fabric via 2 connections each
>
> So the connection from the Server to the library is not the bottleneck.  I
> have 4 drives going down 1 fibre path and 4 down the other.  Considering
> 1gb FC can do 100MB/sec, and an LTO drive does 15MB/sec, that means a max
> througput of 60MB/sec per FC port.

Minor correction: that's the uncompressed speed.  If you're doing
compression on your drives, which you should be, you could theoretically
push that up to 120mB/sec.  Realistically I've seen LTO drives hit
20mB/sec each.  Also, the SBUS cards on the E4000's aren't known for the
best throughput so they could be part of your problem.

[snip]

> So how do I scale the solution to open the ethernet bottleneck?  Veritas is
> not being forthcoming with a solution, and I can't seem to find any best
> practices documents on their site with any insight.

This is just the sort of thing SSO was designed to handle.  You don't have
to put all of your large servers on the SAN and make them media servers as
long as they're all served by gigabit ethernet.  You could pick another
machine or two to make media servers or, if you want to keep the load off
of your production machines, buy a new box just for this purpose.  Each
tape drive can only talk to one media server at a time, but if your
master/media is backing up 5 hosts, your new media server could be backing
up 5 more or whatever.

> Should I consider trunking ethernet to my Extreme switches?

You could, but you would still be limited by the throughput of a single
media server.

> What about running a media server but controlling the robot from the master?

That's SSO.  One machine controls the robot while the others make requests
of it to move tapes but talk directly to the LTO drives.

> Has anyone had any experience with Vertias's claim that they can do "SAN
> direct" backups?  ie,Direct Server -> TL over FC without using IP over FC

That works like a champ.  What does not work, though, is RAID unit -> TL
without going through a media server.  That's been pie in the sky for
several years now and will probably stay that way for a while.

If you have any specific questions let me know.  I work for a storage
integrator/reseller so this is what I do for a living.  I've seen quite a
number of installations where the LTO drives are not native fiber and they
work quite well.  Until about eight or ten months ago LTO and fiber were a
bad combination due to instability, lack of interoperability, etc , but it
has come a long way since then.  Our LTO installs are rock solid even with
fiber/SCSI bridges.

-- 
-Jason

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