Question about iSCSI / NAS / Cluster

[Francisco Cabrita]

Hi,

I don't know if this ML is the right place to post a question about
NAS/iSCSI and Cluster related issue. I will write it anyway.

info:
I have built a NAS server under FreeBSD. Geom RAID5 over 3 hard disks and
iSCSI target0 created.
It is up and running without problems "exporting" a SCSI driver to a Ms
Windows 2000 Server with Microsoft iSCSI Inititator driver.
The volume is NTFS.

doubt:
I have read multiple "old" posts around the web that I can't connect
multiple initiators (w2k clients) to the same target. Is this true nowadays?

Facts:
I really need at least two w2k clients to the same "storage NAS". Any tip
about how to solve this?
Maybe some kind of failover technique between both w2k servers?

I really appreciate your help. Thanks in advance

Best Regards
Francisco

PS: I sent this email to freebsd-scsi ML too. No anwsers until now.

--
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http://www.linkedin.com/in/franciscocabrita
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[Francisco Cabrita]

I've received a reply from John Nielsen via freebsd-scsi ML.

"...

Hi John,

I first want to say many thanks for your reply.

On Mon, May 25, 2009 at 3:56 PM, John Nielsen <lists@...> wrote:

> On Monday 25 May 2009 09:30:40 am Francisco Cabrita wrote:
> > info:
> > I have built a NAS server under FreeBSD. Geom RAID5 over 3 hard disks
> > and iSCSI target0 created.
> > It is up and running without problems "exporting" a SCSI driver to a Ms
> > Windows 2000 Server with Microsoft iSCSI Inititator driver.
> > The volume is NTFS.
> >
> > doubt:
> > I have read multiple "old" posts around the web that I can't connect
> > multiple initiators (w2k clients) to the same target. Is this true
> > nowadays?
>
> You do not want two machines to have write access to the same SCSI device
> at the same time unless you use a filesystem designed for such access.
> NTFS is not such a filesystem. Just hooking two win2k boxes to the same
> iSCSI target to do NTFS will cause problems.

yep I had such problems.


>
>
> Alternatives:
> Microsoft clustering (two or more nodes coordinate to provide certain
> services, the disk volume is only active on one of them at any given
> time)


I need to seek a Windows expert down here :)


>
> Some real clustered filesystem designed for shared access. I don't know of
> any for Windows off the top of my head but I haven't ever looked in to
> it.
> Use the setup you have already with one w2k client, then use Windows
> filesharing to export the volume to other clients.
> Avoid the middleman, drop iSCSI and just use Samba on the NAS box. (Or NFS
> if you want to dabble in Microsoft's Services for Unix... (cue scary
> music))


In another company I have another FreeBSD NAS exporting a NFS volume to
another FreeBSD Samba server, on wich I share some directories to Ms XP
clients. I have no iSCSI on it and it's just fine. Almost 3 years up and
running.

Avoiding iSCSI it's a nice possibility but, on this new scenario the volumes
are exported to both w2k PDC and w2k BDC. My client relies upon a very
granular permission scheme. I don't know if I can handle this without a NTFS
volume. (If I'm not wrong, we can't format a NTFS partition under FreeBSD)


>
>
> > Facts:
> > I really need at least two w2k clients to the same "storage NAS". Any
> > tip about how to solve this?
> > Maybe some kind of failover technique between both w2k servers?
>
> This is similar to the MS clustering option, there may be more manual ways
> to achieve the same effect.


I prefer not to use manual tasks.


>
> > I really appreciate your help. Thanks in advance
> > PS: I am thinking about sending this email to FreeBSD Cluster ML too.
>
> Note that if you want to stick with iSCSI on the FreeBSD side then your
> questions are really Microsoft-centered, so non-FreeBSD resources may be
> more appropriate. Questions about configuring your FreeBSD storage box to
> allow concurrent access by multiple clients that happen to be running
> Windows would be appropriate on the FreeBSD-questions mailing list.


Yes you are totally right. I just want to say I am truly grateful about your
reply because my primary doubt was about the possibility or not to "map"
multiple initiators to one target. And, where is the best place to ask a
thing and get a really valid answer? yep FreeBSD ML :)

I will try to explore your tips about MS Clustering.

Once again Thanks
Francisco Cabrita



JN

..."

On Mon, May 25, 2009 at 3:39 PM, Francisco Cabrita <
francisco.cabrita@...> wrote:

> Hi,
>
> I don't know if this ML is the right place to post a question about
> NAS/iSCSI and Cluster related issue. I will write it anyway.
>
> info:
> I have built a NAS server under FreeBSD. Geom RAID5 over 3 hard disks and
> iSCSI target0 created.
> It is up and running without problems "exporting" a SCSI driver to a Ms
> Windows 2000 Server with Microsoft iSCSI Inititator driver.
> The volume is NTFS.
>
> doubt:
> I have read multiple "old" posts around the web that I can't connect
> multiple initiators (w2k clients) to the same target. Is this true nowadays?
>
> Facts:
> I really need at least two w2k clients to the same "storage NAS". Any tip
> about how to solve this?
> Maybe some kind of failover technique between both w2k servers?
>
> I really appreciate your help. Thanks in advance
>
> Best Regards
> Francisco
>
> PS: I sent this email to freebsd-scsi ML too. No anwsers until now.
>
> -- <http://www.linkedin.com/in/franciscocabrita>
>

Any aditional tips are welcome, meanwhile thanks anyway. :)

Best regards,
Francisco Cabrita
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[Bob McClure]

Francisco,
  This sounds very similar to the issue I encountered when trying to backend
a shared SAN connection. The problem that
I ran into was that this shared area would need to be configured as a shared
file system such as GFS that is not available
for FreeBSD. I did get concurrent connections, but bad things happened.

  There is package that is available for FreeBSD (ifstated) that reportedly
will aid you with knowing when a carp status changed, but
I personally never got it to work properly due to time constraints.

  My original solution that I still use is a script that looks at the carp
device info from ifconfig and reports MASTER or BACKUP.
This can be executed periodically by a script to have the new master mount
the shared resource and the non-master give it up.
This is far from ideal, but works in instances where immediate fail over is
not required. This is designed to be called from a shell
script via backtick.

STATUS=`./carpstatus.pl`
if [ $STATUS = "MASTER" ] ; then
.....
fi

(carpstatus.pl)
#!/usr/bin/perl
# $output = `ifconfig | grep carp: | grep vhid | /usr/bin/awk '{print \$2}'`
;
# chomp($output) ;
# print "$output" ;

  I hope this helps you with your issue.

Bob McClure



On Mon, May 25, 2009 at 9:39 AM, Francisco Cabrita <
francisco.cabrita@...> wrote:

> Hi,
>
> I don't know if this ML is the right place to post a question about
> NAS/iSCSI and Cluster related issue. I will write it anyway.
>
> info:
> I have built a NAS server under FreeBSD. Geom RAID5 over 3 hard disks and
> iSCSI target0 created.
> It is up and running without problems "exporting" a SCSI driver to a Ms
> Windows 2000 Server with Microsoft iSCSI Inititator driver.
> The volume is NTFS.
>
> doubt:
> I have read multiple "old" posts around the web that I can't connect
> multiple initiators (w2k clients) to the same target. Is this true
> nowadays?
>
> Facts:
> I really need at least two w2k clients to the same "storage NAS". Any tip
> about how to solve this?
> Maybe some kind of failover technique between both w2k servers?
>
> I really appreciate your help. Thanks in advance
>
> Best Regards
> Francisco
>
> PS: I sent this email to freebsd-scsi ML too. No anwsers until now.
>
> --
> blog: http://sufixo.com/raw
> http://www.linkedin.com/in/franciscocabrita
> _______________________________________________
> freebsd-cluster@... mailing list
> http://lists.freebsd.org/mailman/listinfo/freebsd-cluster
> To unsubscribe, send any mail to "freebsd-cluster-unsubscribe@..."
>

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[Francisco Cabrita]

Hi Bob,

Thanks for your reply :)


On Mon, May 25, 2009 at 5:25 PM, Bob McClure <h8msft@...> wrote:

> Francisco,
>   This sounds very similar to the issue I encountered when trying to
> backend a shared SAN connection. The problem that
> I ran into was that this shared area would need to be configured as a
> shared file system such as GFS that is not available
> for FreeBSD. I did get concurrent connections, but bad things happened.


Yep and those bad things did happen...(love backups)
Yes that's sad we don't have such GFS but maybe CodaFS will be ready to
production one day.
(I have no idea how about MogileFS is regarding distributed FS under
FreeBSD)


>
>
>   There is package that is available for FreeBSD (ifstated) that reportedly
> will aid you with knowing when a carp status changed, but
> I personally never got it to work properly due to time constraints.


I know and I use ifstated to switch from Cable to ADSL Internet providers.
It's a KISS solution. I didn't even think using it on this scenario... :)
gonna think about it.


>
>   My original solution that I still use is a script that looks at the carp
> device info from ifconfig and reports MASTER or BACKUP.
> This can be executed periodically by a script to have the new master mount
> the shared resource and the non-master give it up.
> This is far from ideal, but works in instances where immediate fail over is
> not required. This is designed to be called from a shell
> script via backtick.


I see. link up for the master; test connection and in case of some network
failure, get that target offline and mount another to slave one.

>
>
> STATUS=`./carpstatus.pl`
> if [ $STATUS = "MASTER" ] ; then
> .....
> fi
>
> (carpstatus.pl)
> #!/usr/bin/perl
> # $output = `ifconfig | grep carp: | grep vhid | /usr/bin/awk '{print
> \$2}'` ;
> # chomp($output) ;
> # print "$output" ;
>
>   I hope this helps you with your issue.

Carp sound really good to this. I was reading about Lagg operating as a
failover but that don't make sense because I want to see and test both links
but use just one at a given time.

Very cool, and thanks very much for your tip! :)

Best regards,
Francisco Cabrita

>
> Bob McClure
>
>
>
> On Mon, May 25, 2009 at 9:39 AM, Francisco Cabrita <
> francisco.cabrita@...> wrote:
>
>> Hi,
>>
>> I don't know if this ML is the right place to post a question about
>> NAS/iSCSI and Cluster related issue. I will write it anyway.
>>
>> info:
>> I have built a NAS server under FreeBSD. Geom RAID5 over 3 hard disks and
>> iSCSI target0 created.
>> It is up and running without problems "exporting" a SCSI driver to a Ms
>> Windows 2000 Server with Microsoft iSCSI Inititator driver.
>> The volume is NTFS.
>>
>> doubt:
>> I have read multiple "old" posts around the web that I can't connect
>> multiple initiators (w2k clients) to the same target. Is this true
>> nowadays?
>>
>> Facts:
>> I really need at least two w2k clients to the same "storage NAS". Any tip
>> about how to solve this?
>> Maybe some kind of failover technique between both w2k servers?
>>
>> I really appreciate your help. Thanks in advance
>>
>> Best Regards
>> Francisco
>>
>> PS: I sent this email to freebsd-scsi ML too. No anwsers until now.
>>
>> --
>> blog: http://sufixo.com/raw
>> http://www.linkedin.com/in/franciscocabrita
>> _______________________________________________
>> freebsd-cluster@... mailing list
>> http://lists.freebsd.org/mailman/listinfo/freebsd-cluster
>> To unsubscribe, send any mail to "freebsd-cluster-unsubscribe@...
>> "
>>
>
>

--
blog: http://sufixo.com/raw
http://www.linkedin.com/in/franciscocabrita
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