Re: [Xen-users] Xen and iSCSI

[tbrown@xxxxxxxxxxxxx]

>
> > what i plan to do (once i get a few test boxes) is to use coraid's AoE
> > protocol (the driver is in the main Linux tree).  it's designed to be
> > software driven, without any special card; and it's CPU utilization seems
> > to be around ATA levels.
>
> I also read about this. My thoughts were that iscsi exists longer and is a
> standard. AoE is no standard and can only be used by linux by now (i think).
> You also can make iscsi targets and initiators without any special hardware.

There is a Linux user-space AoE "server" (vblade), but in my experience
read performance sucks (5 MByte/s), write performance was fine (40+ MB/s).
I had a look at the CorRAID site and they seemed to show the slow numbers,
so I am still looking elsewhere for a good network attached "block
device"...

[I suspect the read performance issue was just an issue with not being
able to handle multiple reads simultaneously, but I'm not strong enough
with kernel space drivers to validate that...]

> > with any kind of SAN, i think the best strategy would be to use CLVM
> > in dom0 and export the logical volumes to the domUs; this way you only
> > have to setup the SAN drivers in dom0, the domUs would treat those as
> > local disks.
>
> Is this safe for migration? How can you get the block device, which is

doesn't sound like it. I started to type the same question.

> exported to the domU, to other Xen hosts when migrating an domU? If all
> could take place in domU (iscsi initiator and rootfs on iscsi) you are
> completly independent from the dom0 block device configuration. I would
> like to prefer this if possible and if performance is not to bad.

AFAICS, performance should be better if the domU attaches directly to the
network storage instead of having to relay all reads/writes through dom0

-Tom



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