Subject: Re: NetBSD iSCSI HOWTOs
To: Aaron J. Grier <firstname.lastname@example.org>
From: Bill Studenmund <email@example.com>
Date: 02/22/2006 17:30:19
Content-Type: text/plain; charset=us-ascii
On Wed, Feb 22, 2006 at 04:42:32PM -0800, Aaron J. Grier wrote:
> On Wed, Feb 22, 2006 at 10:19:46PM +0000, Alistair Crooks wrote:
> > I'm working on a NetBSD initiator, but it won't be in 4.0.
> I'm thinking a RAID of iSCSI targets would be interesting.
Yep, it is.
Though don't add too many boxes to the RAID as you then get TCP problems.=
David Nagle, at Panasas, described the problem to me at FAST and refered=20
to it as "In-cast", the opposite of multicast. If a lot of senders (iSCSI=
targets talking to an initiator) flood a receiver, packets get dropped and=
TCP goes into recovery. For a striped read, you then end up having the=20
whole operation wait for one connection to recover. There's probably a PhD=
dissertation in all of this. :-)
Where exactly "too many" is at depends on the drives you have in each box=
and your network. Look hard at the receiving NIC in the initiator.=20
Depending on how beefy the iSCSI targets are, you may need 10G ethernet.
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