[Linux-cluster] Software Iscsi with Redhat Cluster

[Tristram Cheer]

Thanks for the reply,

So i take it that you are exporting LVM volume groups? i'm tring to 
avoid placing many services on the cluster so avoiding CLVM is a big one 
for me. I was planning on exporting the Logical Volumes, about 28 or so 
in total via iSCSI.

The reason for avoiding Cluster Suite for anymore than GFS is that with 
XEN (3 real servers, 9 virtual ones) that the cluster can stop 
functioning correctly if all the virtual servers go down but the 
physical ones remain working fine. I'm yet to find a way to stop the 
virtual servers bringing down the whole cluster - this may be possable 
but i'm rather new to RHCS :)

Cheers

Tristram

Ryan Thomson wrote:

>Hi Tristram,
>
>I'm just about to put a completely Linux based software iSCSI RedHat
>Cluster with GFS into production. We have four RHEL4AS machines acting as
>cluster nodes and an 8TB RHEL4AS server is exporting disk as two
>arrays/iSCSI targets to the cluster nodes. Several more storage boxes we
>already own (previously Linux servers exporting large arrays over NFS) are
>to be added as iSCSI targets.
>
>I am using the iSCSI initiator that comes with RHEL4U2, the cisco open
>source one it is I believe. For targets, I'm using the iSCSI Enterprise
>Target (http://sourceforge.net/projects/iscsitarget/). The only thing I
>found so far that doesn't seem to work is the iSCSI alias. I can't seem to
>get the alias I set in the target to show up on the initiator. I don't
>know if the problem is the target or the initiator as I haven't found
>anything online yet about this issue. The currently available Linux iSCSI
>software seems to work pretty much flawlessly for me otherwise.
>
>So far it's been quite easy and painless setting up CLVM volumes and
>putting GFS on them, I even wrote a basic wrapper script to do all the
>work for me, streamlining the proceedure. Filesystem expansion seems to
>work as expected. I haven't played with snapshots.
>
>Initial numbers show transfer rates from end to end (NFS clients to
>Cluster NFS server to GFS) to be better for iSCSI than GNBD. Keep in mind
>these are initial tests using bonnie++ and using 'time' to time file
>copies of various sizes, nothing concrete. I suspected NFS to be a
>bottleneck but it seems that storage interconnect/fabric protocol still
>makes a difference even with NFS being crappy to the clients.
>
>>From cluster nodes to storage I found transfer rates to be near local max
>with iSCSI, again don't trust me though, do you own tests. My hardware
>doesn't have very high end disk, just SATA with 3ware 9500 cards. I didn't
>do the cluster node to storage test with GNBD :(
>
>Anyways, so far my initial experience has been great. I solved an issue
>causing my cluster nodes to kernel panic and ever since, it's been running
>very well serving Apache, MySQL, OpenLDAP and NFS exports. I haven't fully
>stress tested it yet as I don't have a workable means to do so right now,
>besides migrating users over slowly.
>
>I have zero experience with Xen so I can't help you there.
>
>I hope that helps.
>
>--
>Ryan Thomson
>Systems Administrator
>University Of Calgary Biocomputing
>http://moose.bio.ucalgary.ca/
>
>  
>
>>Hi all,
>>
>>is anyone in a production setting using software Iscsi Targets and
>>Initiators as a side options to GNBD? i'm exploring all our options for
>>a Xen/Cluster Suite n+2 server setup for our ISP and would like to hear
>>peoples thoughts on the best option, rather than using a SAN with FC we
>>have decided to go with a Intel Raid Array with standard linux to reduce
>>inital costs and need to find out what people are using in production to
>>export block devices.
>>
>>Thanks in advance
>>
>>Tristram
>>
>>--
>>Linux-cluster mailing list
>>Linux-cluster at redhat.com
>>https://www.redhat.com/mailman/listinfo/linux-cluster
>>
>>    
>>
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