[OpenAFS] Iscsi or san support.

[Hartmut Reuter]

Dennis O. Aliev wrote:
> Hello,
>=20
> I'm new to openafs and would like to get a more clear picture after rea=
ding documentation.
>=20
> Is it possible to have client hosts access data directly from SAN type =
device (iSCSI in our case) instead of using openafs server?
>=20
> Thank you.
>=20

I am working on a project which allows direct access from trusted=20
clients to visible
fileserver partitions. It should not matter by which means these=20
partitions are visible
(SAN or GPFS or NFS or Lustre or whatever).

The technique is the following:

When the client starts it looks for /vicep-partitions. These partitions=20
are marked by
the fileserver with a copy of the sysid-file (from /usr/lafs/local).=20
Afsd communicates
this information into the kernel memory of the client. Whenever a file=20
is going to be
accessed on from a fileserver who's uuid had been found in  the sysid=20
file a new
RPC is used to get the information about the file's path inside the=20
/vicep partition
from the fileserver. Of course, all permission checks as for StoreData=20
or FetchData
are done by the fileserver before returning the path information. Now=20
the client tries
to open the file directly. When this is successfu, all f=FArther I/O to=20
the file is done
bypassing the cache and the fileserver. Callbacks from the fileserver=20
force a
re-evaluation so that moving of volumes remains still possible without
loss of access from the client.

First results show native filesystem performance ~100 MB/s for large=20
files on
raid systems or GPFS. It is considered to be used in High Performance=20
Computing
clusters such as Regatta systems on a Federeation switch or Linux cluster=
s.

This feature is still under test here, not in real production.

Hartmut
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Hartmut Reuter                           e-mail reuter@rzg.mpg.de
					   phone +49-89-3299-1328
RZG (Rechenzentrum Garching)               fax   +49-89-3299-1301
Computing Center of the Max-Planck-Gesellschaft (MPG) and the
Institut fuer Plasmaphysik (IPP)
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