Great summary Michael.
I have a few questions on what a "shared filesystem" hardware
CAN be:
- iSCSI storage ? (cheap GigaEthernet SAN)
according to Wikipedia http://en.wikipedia.org/wiki/ISCSI ,
only 1 iSCSI-client can be connected to 1 iSCSI-server (disk)
at a time...so this does not allow for a shared FS ?
- Fibre Channel SAN with NFSv4, GSF support
- NAS with with NFSv4, GSF support
- if GFS is mainly for Linux, any NAS or SAN should work ??
regards,
Michael Menge wrote:
- Shared filesystem Active/Passive
This setup can add HA to a normal Cyrus server by storing the Mails and
databases on a shared filesystem and monitoring the server with
heartbeat.
This setup should work with every shared filesystem and there should
be no
problems with bdb
- Shared filesystem Active/Active
In this setup all users are on all server. The mailboxes and databases
are on a shared filesystem so that changes on one server are visible
on all
other servers. Cyrus depends on the file-locking of the filesystem.
NFSv4,
GFS, Lustre, and some other shared filesystem affirm that they have
file-locking across cluster nodes.
The sockets, lock- and pid-files have to stay on a local
filesystem or have to be made unique across cluster nodes.
BDB seems to have problems in this setup, because the changes of the lock
in the mmaped files are not instantly on all clients/nodes and the use of
shared memory. You have to compile Cyrus without bdb-support to get
rid of
the errors. This setup needs no extra servers, and all use the same
configuration. In case of server crash the user use one of the other
servers.
The server can be replaced with an clone of one of the other servers.
The storage should be too on a HA cluster to make the whole
mailsystem ha.
The Active/Active Shared filesystem setup is discussed controvers.
This setup is not widely used and therefor not tested that mutch.
But Dave McMurtrie and Scott Adkins have reported of sucsessfull
installations
The following shared Filesystems seem support the file-locking
GFS http://sources.redhat.com/cluster/gfs/
Lustre http://www.lustre.org/
NFSv4 http://www.nfsv4.org/
Polyserve CFS http://www.polyserve.com
Veritas CFS
http://www.symantec.com/enterprise/products/overview.jsp?pcid=1020&pvid=209_1
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Universitaet Tuebingen Fax.: (49) 7071/29-5912
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Waechterstrasse 76
72074 Tuebingen
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Marcelo Maraboli Rosselott
Jefe Area de Redes y Comunicaciones (Network & UNIX Systems Engineer)
Ingeniero Civil Electronico, CISSP (Electronic Engineer, CISSP)
Direccion Central de Servicios Computacionales (DCSC)
Universidad Tecnica Federico Santa Maria phone: +56 32 2654071
Chile. http://www.usm.cl http://elqui.dcsc.utfsm.cl
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