[TriLUG] iscsi setup

[OlsonE at aosa.army.mil]

In addition, it is highly advised to either segment out your iSCSI
network on a VLAN, or a private switch.  

-----Original Message-----
From: trilug-bounces at trilug.org [mailto:trilug-bounces at trilug.org] On
Behalf Of Ben Pitzer
Sent: Monday, September 25, 2006 10:59 AM
To: Triangle Linux Users Group discussion list
Subject: Re: [TriLUG] iscsi setup

You could say I've done it once or twice.  So basically, here's the deal
on the iSCSI options that you have:

1. Software initiator, native TCP stack
      Pro:  Free, functional, typically fairly stable so long as you
have a solid initiator software
      Con:  Just getting access to your disks, before you even do any
I/O, puts a load on your proc and memory 2. Software initiator, TOE (TCP
offload engine) card
      Pro: Still somewhat inexpensive.  Offloads all of the TCP work to
the TOE card.  No native stack, so less system load for disk access.
TOE cards can also be used for things other than iSCSI, so hardware
costs are not completely lost if you go another direction.
      Con:  Still some load on the system from the initiator software.
TOE cards aren't exactly cheap.  Must confirm the TOE card's
compatibility with your OS.
3.  iSCSI HBA card
      Pro:  Fast.  All of the iSCSI and TCP work are done on the card.
Also usually pretty stable.
      Con: Expensive.  This can cost you almost as much as a fiber HBA.
They only work at GigE.  They also can't be used for any other purpose
if you decide to scrap the IP SAN later on.

So cost and feasibility are required studies here.  Additionally, keep
in mind that many vendors do not support IP link aggregation (NIC
teaming, port bonding, whatever you want to call it) for IP SAN
implementations.  Given the nature and sensitivity of the signal on the
wire, I would not recommend using an IP SAN over a 10/100 network.  GigE
is the way to go, period.
Remember, this is a local disk so far as the OS is concerned, so the
faster the media between host and disk the better.

As far as backing up your iSCSI target LUN, it will depend on the
vendor.
NDMP will transfer at the block level, so that might be your best bet.
It'll depend on what you're backing up, and where to.  What type of IP
SAN target vendor are you looking at?  NetApp?  EMC?  OpenFiler?
Somebody else?  We can talk about this more directly if you want.  Just
let me know off list.

-Ben Pitzer


On 9/24/06, Jason Tower <jason at cerient.net> wrote:
>
> anyone have experience with iscsi on linux (both initiators and
targets)?
> trying to find out some best practices for running a backend server 
> (iscsi
> target) to multiple clients (initiators).  any significant pros/cons 
> to using iscsi specific hardware HBAs?  the transport will probably be

> 100mb ethernet to start, moving to gigabit as needed.
>
> also, what options exist for backing up my primary iscsi target to 
> another system?  are there tools that provide rsync-like capabilities 
> but at the block instead of the file level?
>
> jason
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