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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