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 <[EMAIL PROTECTED]> 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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