[Stgt-devel] [Iscsitarget-devel] Re: stgt a new version of iscsi target?
michaelc at cs.wisc.edu
Wed Dec 14 20:55:53 CET 2005
Vladislav Bolkhovitin wrote:
> Mike Christie wrote:
>>> Are you sure that there are no now or will be available in the
>>> nearest feature such (eg iSCSI) SCSI arrays with response
>>> time/latency so small that having 5 (five) context switches or more
>>> per command, some of which include map/unmap operations, will not
>>> increase the latency too much? I mean, eg NFS server, which
>>> originally was user space daemon and many people didn't want it in
>>> the kernel. Eventually, it's in. I don't see any fundamental
>>> difference between NFS server and SCSI target server,
>> Isn't the reason a NFS server is still in the kernel is becuase some
>> of the locking difficulties?
> Might be. But from what I remember, the major reason was the
> performance. After googling a bit I found many acknowledgments of that.
I do not think we are going to get anywhere with this type of thread :(
We should try to compare at least one of the userspace *nbd
implementations with the unh target in scst. I see some that just do
some basic socket ops (no sendfile type hook in even) for the network
part then just async or normal read/writes. I do not want to comapre FC
to nbd, but maybe comparing software iscsi to userspace nbd is a little
more fair. I think ata over ethernet has a userspace target too. Is the
unh target defaults set ok for performance testing, or could you send
some off list, so we can at least test those.
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