AoE - ATA over ethernet

[Howell]

What maddness is this? : )

http://en.wikipedia.org/wiki/ATA_over_Ethernet

This kinda makes a managed switch mandatory?

 

[Gilbo]

Ya, it's really inflexible. It's basically designed to maximize performance by removing the overhead of the TCP/IP stack (vs. iSCSI). You also don't to translate ATA commands to SCSI and back again if you use ATA disks. (Although I think, for SATA drives, Linux runs everything through SCSI anyway? Hence they appear as sd*...).

Clearly removing the TCP/IP stack has a lot of collateral damage for the sake of performance. In fact, the architecture kind of defeats the purpose. In such a situation, trying to maximize performance on a local segmented network, most people would use fibre channel. The use case for ATAoE is pretty small. It's useful if you want to save money on cables by using standard Cat5e or Cat6 over fibre channel and not sacrifice too much performance, or, if you have run lengths better served by running ethernet cable than fibre channel cables. Otherwise, there really isn't much point.

I guess it's useful in clusters? Save cash, don't lose too much performance? But you have to run an extra set of GbE? I'm sure there's a point somewhere...

 

[sechs]

I was given to the impression that 10G ethernet was supplanting fibre channel.

 

[Howell]

HyperSCSI is the SCSI equivalent to AoE.

ATA disks are cheaper but surely there is more to it than that.

 

[Gilbo]

I was given to the impression that 10G ethernet was supplanting fibre channel.

ATAoE with 10GbE would have advantages over fibre channel. That's a better use case.

 

[Pradeep]

I was given to the impression that 10G ethernet was supplanting fibre channel.

We wil be using 10GB links to connect our gigabit switches to the core (Cisco 4948-10s).

But from where I sit 4GB FC is still doing just fine. Most hosts will make do with 1 or 2GB links anyway. In this case FC for SAN connectivity. 10GB port costs are still quite significant.

 

[sechs]

I don't suspect that ethernet will overtake FC anywhere near overnight, but it seems that the ethernet technology will be cheaper at the high-end. When you can use the same stuff for SANs and general data (even if segregated networks), it ends up being cheaper.

 

[Onomatopoeic]

What maddness is this? : )
http://en.wikipedia.org/wiki/ATA_over_Ethernet

Ethernet cabling and transceivers is Layer 1 and ATA command set is Layer 2.

This kinda makes a managed switch mandatory?

You want to build VLANs for your AOE SAN for the same reasons you want zone you F-C SAN.

ATAoE with 10GbE would have advantages over fibre channel.

Not really. F-C (loop and fabric protocols) are lossless, Ethernet in its present state is not lossless.

But fear not Ethernet lovers, so-called "Datacenter Ethernet" (an IEEE standard) is coming along someday (haven't heard much about it in well over a year now). This new type of Ethernet will have both new and updated signaling protocols to complement existing Ethernet protocols. To fully implement Datacenter Ethernet, you will need shiny new (and I'm sure, expensive) Datacenter Ethernet switches, routers, and HBAs. But, wisely, Datacenter Ethernet hardware will also be able to handle "old" Ethernet traffic.

Incredibly, what caused the Datacenter Ethernet effort was a subset of Fibre-Channel vendors that saw the writing on the wall as far as the probable future of Fibre-Channel would surely be if nothing was done. They correctly saw the slow-but-sure ganging up on F-C technology by the unholy alliances of SCSI and ATA (in SAS / SATA cooperative technologies), then Ethernet (iSCSI and AOE), and more recently InfinBand -- which recently added iSCSI as a natively-supported protocol within InfiniBand. F-C began to face a war from the bottom of the market and now at the top as well.

Once this new standard finally gets pushed out of the IEEE Ethernet committee, F-C will be able to run over Ethernet LAN and MAN topologies with "standard" Ethernet equipment.

But from where I sit 4GB FC is still doing just fine. Most hosts will make do with 1 or 2GB links anyway.

Many servers can barely saturate a 2 Gb/s F-C link (block data) because of the inefficient 1 Gb/s Ethernet link (packet data) connecting the users to the server.