Rescan for new LUNs

Rescan for new LUNs

[Allen, Jack]

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Hello: 
        What is the best way to cause the system to rescan for new LUNs,
other than rebooting? 

----- 
Jack Allen 


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Re: Rescan for new LUNs

[Malahal Naineni]

Allen, Jack [Jack.Allen@mckesson.com] wrote:
>    Hello:
>            What is the best way to cause the system to rescan for new LUNs,
>    other than rebooting?

Writing something to some files in sysfs. If none of the LUNs are in
use, "modprobe -r <module>" followed by "modprobe <module>" will also
work.

Thanks, Malahal.

Re: Rescan for new LUNs

[Oren Held]

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It's not an easy process.

The rescan-scsi-bus.sh script was added in recent RHEL5 updates, already 
in old SLES. I guess it's becoming kind of a standard.

On 07/01/10 04:00, Allen, Jack wrote:
>
> Hello:
> What is the best way to cause the system to rescan for new LUNs, other 
> than rebooting?
>
> -----
> Jack Allen
>
>
> --
> dm-devel mailing list
> dm-devel@redhat.com
> https://www.redhat.com/mailman/listinfo/dm-devel


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Re: Rescan for new LUNs

[Allen, Jack]

 

-----Original Message-----
From: dm-devel-bounces@redhat.com [mailto:dm-devel-bounces@redhat.com] On Behalf Of Malahal Naineni
Sent: Wednesday, June 30, 2010 9:08 PM
To: dm-devel@redhat.com
Subject: Re: [dm-devel] Rescan for new LUNs

Allen, Jack [Jack.Allen@mckesson.com] wrote:
>    Hello:
>            What is the best way to cause the system to rescan for new LUNs,
>    other than rebooting?

Writing something to some files in sysfs. If none of the LUNs are in
use, "modprobe -r <module>" followed by "modprobe <module>" will also
work.

Thanks, Malahal.

===========
Something to some file is not very helpful. And the other LUNs are in use. I am just trying to keep from having to reboot if I really do not need to.

----
Jack Allen

Re: Rescan for new LUNs

[Allen, Jack]

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That sounds more like what I am looking for. But I can not find the
script on my system or what provides it via "yum provides". I am running
RHEL 5.5.
 
We have customers that run an Application that needs to be up 24*7. They
some times need to add additional storage and when attached to a SAN
they would prefer not to have to take the Application down and reboot
the system just to make the new LUNs be seen by the system.
-----
Jack Allen
 


  _____  

From: dm-devel-bounces@redhat.com [mailto:dm-devel-bounces@redhat.com]
On Behalf Of Oren Held
Sent: Thursday, July 01, 2010 2:55 AM
To: dm-devel@redhat.com
Subject: Re: [dm-devel] Rescan for new LUNs


It's not an easy process.

The rescan-scsi-bus.sh script was added in recent RHEL5 updates, already
in old SLES. I guess it's becoming kind of a standard.

On 07/01/10 04:00, Allen, Jack wrote: 

Hello: 
        What is the best way to cause the system to rescan for new LUNs,
other than rebooting? 

----- 
Jack Allen 



--

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dm-devel@redhat.com <mailto:dm-devel@redhat.com> 

https://www.redhat.com/mailman/listinfo/dm-devel
<https://www.redhat.com/mailman/listinfo/dm-devel> 



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Re: Rescan for new LUNs

[Malahal Naineni]

Allen, Jack [Jack.Allen@mckesson.com] wrote:
> Something to some file is not very helpful. And the other LUNs are in
> use. I am just trying to keep from having to reboot if I really do not
> need to.

I said what I said because the exact file depends on how your LUN is
connected. Here is some useful info though! For each scsi host, there
should be a sysfs file "/sys/class/scsi_host/hostN/scan". If you know
the exact host number, say "2", then you can do the following to rescan:

echo '- - -' > /sys/class/scsi_host/host2/scan

If you don't know the host number, then try on all of them.

Thanks, Malahal
PS: try running 'find /sys -name scan' to get all the files and chose
what ever you want to scan.

Re: Rescan for new LUNs

[Bryn M. Reeves]

On 07/01/2010 06:43 PM, Allen, Jack wrote:
> That sounds more like what I am looking for. But I can not find the script on my 
> system or what provides it via "yum provides". I am running RHEL 5.5.
> We have customers that run an Application that needs to be up 24*7. They some 
> times need to add additional storage and when attached to a SAN they would 
> prefer not to have to take the Application down and reboot the system just to 
> make the new LUNs be seen by the system.
> -----
> Jack Allen
> 
> --------------------------------------------------------------------------------
> *From:* dm-devel-bounces@redhat.com [mailto:dm-devel-bounces@redhat.com] *On 
> Behalf Of *Oren Held
> *Sent:* Thursday, July 01, 2010 2:55 AM
> *To:* dm-devel@redhat.com
> *Subject:* Re: [dm-devel] Rescan for new LUNs
> 
> It's not an easy process.
> 
> The rescan-scsi-bus.sh script was added in recent RHEL5 updates, already in old 
> SLES. I guess it's becoming kind of a standard.

The script was originally written by Kurt Garloff but it's been included
in the sg3_utils tarball for years:

Changelog for sg3_utils-0.99 [20020317]
----------------------------
  - add 'fua' and 'sync' arguments to sg_dd, sgp_dd and sgm_dd
  - improve sg_inq, add "-cl" and "-36" arguments
  - add sg_modes + sg_logs for MODE SENSE and LOG SENSE queries
  - add rescan-scsi-bus.sh [Kurt Garloff] to archive director

It's only recently been included in the build for RHEL packages though
(5.3 iirc) - just yum install sg3_utils to get the script on a RHEL-5
system (as well as other useful bits like sg_map and friends).

The script may work for some combinations of storage and controller in
earlier RHEL versions but isn't included in the distribution and is not
always perfectly reliable.

If you need to add/remove storage on these older releases you can use
the simple scsi-add/remove-single-device interface via /proc/scsi/scsi.

If you have access to the Red Hat knowledge base (RHN login) there's an
article that explains the options on RHEL systems:

https://access.redhat.com/kb/docs/DOC-3942

And there's the RHEL5 Online Storage Reconfiguration Guide here:

http://tinyurl.com/ya6wmce [www.redhat.com]

That documents these interfaces as well as the FC and iSCSI APIs and
their relation to other components such as multipath.

Regards,
Bryn.

Re: Rescan for new LUNs

[brem belguebli]

echo '- - -' > /sys/class/scsi_host/hostX/scan should be enough to
discover new Luns.

For some unknown reason, with some specific SAN storage  arrays (HP XP
in my case) , for newly SAN connected servers (new  zoning), it is not
enough.

I have to  issue lip (loop init) to my FC hosts

echo 1 > /sys/class/fc_host/hostX/issue_lip

This lip command can be destructive(and is asynchronous) , so use it
only before first SAN discovery. After that as I said, scan is enough.

Brem

2010/7/6 Bryn M. Reeves <bmr@redhat.com>:
> On 07/01/2010 06:43 PM, Allen, Jack wrote:
>> That sounds more like what I am looking for. But I can not find the script on my
>> system or what provides it via "yum provides". I am running RHEL 5.5.
>> We have customers that run an Application that needs to be up 24*7. They some
>> times need to add additional storage and when attached to a SAN they would
>> prefer not to have to take the Application down and reboot the system just to
>> make the new LUNs be seen by the system.
>> -----
>> Jack Allen
>>
>> --------------------------------------------------------------------------------
>> *From:* dm-devel-bounces@redhat.com [mailto:dm-devel-bounces@redhat.com] *On
>> Behalf Of *Oren Held
>> *Sent:* Thursday, July 01, 2010 2:55 AM
>> *To:* dm-devel@redhat.com
>> *Subject:* Re: [dm-devel] Rescan for new LUNs
>>
>> It's not an easy process.
>>
>> The rescan-scsi-bus.sh script was added in recent RHEL5 updates, already in old
>> SLES. I guess it's becoming kind of a standard.
>
> The script was originally written by Kurt Garloff but it's been included
> in the sg3_utils tarball for years:
>
> Changelog for sg3_utils-0.99 [20020317]
> ----------------------------
>  - add 'fua' and 'sync' arguments to sg_dd, sgp_dd and sgm_dd
>  - improve sg_inq, add "-cl" and "-36" arguments
>  - add sg_modes + sg_logs for MODE SENSE and LOG SENSE queries
>  - add rescan-scsi-bus.sh [Kurt Garloff] to archive director
>
> It's only recently been included in the build for RHEL packages though
> (5.3 iirc) - just yum install sg3_utils to get the script on a RHEL-5
> system (as well as other useful bits like sg_map and friends).
>
> The script may work for some combinations of storage and controller in
> earlier RHEL versions but isn't included in the distribution and is not
> always perfectly reliable.
>
> If you need to add/remove storage on these older releases you can use
> the simple scsi-add/remove-single-device interface via /proc/scsi/scsi.
>
> If you have access to the Red Hat knowledge base (RHN login) there's an
> article that explains the options on RHEL systems:
>
> https://access.redhat.com/kb/docs/DOC-3942
>
> And there's the RHEL5 Online Storage Reconfiguration Guide here:
>
> http://tinyurl.com/ya6wmce [www.redhat.com]
>
> That documents these interfaces as well as the FC and iSCSI APIs and
> their relation to other components such as multipath.
>
> Regards,
> Bryn.
>
> --
> dm-devel mailing list
> dm-devel@redhat.com
> https://www.redhat.com/mailman/listinfo/dm-devel
>