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RE: [Xen-users] AoE vs iSCSI

  • To: "Chris 'Xenon' Hanson" <xenon@xxxxxxxxxxxxxx>, <xen-users@xxxxxxxxxxxxxxxxxxx>
  • From: Jeff Sturm <jeff.sturm@xxxxxxxxxx>
  • Date: Thu, 11 Mar 2010 19:06:18 -0500
  • Cc:
  • Delivery-date: Thu, 11 Mar 2010 16:08:36 -0800
  • List-id: Xen user discussion <xen-users.lists.xensource.com>
  • Thread-index: AcrBTIwxWVwdOt8pTmiucR0glFm9aAAKPTmQ
  • Thread-topic: [Xen-users] AoE vs iSCSI

> -----Original Message-----
> From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx [mailto:xen-users-
> bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Chris 'Xenon' Hanson
> Sent: Thursday, March 11, 2010 1:56 PM
> To: xen-users@xxxxxxxxxxxxxxxxxxx
> Subject: [Xen-users] AoE vs iSCSI
>   I'm thinking about adding some external mass storage to my Xen
system, and I see
> a
> number of 1U (I pay by the U at my colo) SAN devices that offer iSCSI.
Not too many
> offer
> AoE. For cheap performance, AoE seems preferable since it has less
overhead. Since
> the SAN
> is going to be right next to the Xen box, the routability of iSCSI
isn't a factor for me.
> Just big, cheap and fast.

I've used CoRAID's AoE products before and recommend them because they
are simple, extremely easy to configure, reliable and inexpensive.  They
have a 1U appliance (SR431) listed in their site for $2,475 USD.  That
said I wouldn't choose AoE over iSCSI (or vice versa) for performance
reasons--with either you should get adequate performance, if properly
configured, and you're going to find that networks are so much faster
than disks that for a small appliance the network doesn't really matter
much--throughput is going to be limited by SATA disk performance.

Do you really want a 1U appliance?  You won't get much storage out of
it.   A 3U appliance can typically support 4x the storage of a 1U unit.

Look for a vendor you like, try the product first if possible, choose
based on features, performance and cost.  The protocol is another
consideration altogether--AoE works great for small Linux-only networks.
If you need more interoperability (i.e. Windows) you'll probably want to
stick with iSCSI.

Using AoE on Linux is about as simple as loading the "aoe" kernel
module.  The module auto-discovers targets by Ethernet broadcast and
makes block devices locally available under /dev/etherd/*.  You can then
add a partition table to the block device, carve it up with LVM, or
pretty much anything you'd do with local storage.  AoE is about as easy
to use as it can possibly be.  (iSCSI on the other hand always has me
scurrying for "man" pages first.)


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