topic Re: Changes to multipath disks in Operating System - Linux

Changes to multipath disks

Andrew Young_2 — Fri, 24 Apr 2009 06:21:57 GMT

Hi

I have a BL460c blade running RHEL 4u7 connected to an EVA8100. Currently I have been using a single LUN but this is now proving inadequate and I need to allocate additional space.

The options available are to increase the existing size of the disk on the EVA or adding another disk onto the EVA for use by this server. Thereafter I could either add it to the existing VG or create a new one.

My first question relates to which is the best option and why? Obviously adding new disk on a seperate VG is the least risky but some sagely advice would be appreciated.

My second question, if I do add an additional disk is there a way of getting RHEL to recognize the disk without rebooting?

Thanks in advance.

Andrew Y

Re: Changes to multipath disks

Steven E. Protter — Fri, 24 Apr 2009 08:51:17 GMT

Shalom,

Present a new LUN.

These systems, whether they run HP-UX or Linux are notorious for having problems recognizing space increases on existing LUNS.

I've struggled with this issue enough times, so learn from my pain.

SEP

Re: Changes to multipath disks

mohamed.bouraoui — Fri, 24 Apr 2009 09:55:52 GMT

Hi friend;
Itâ s preferable to add another disk via another controller of EVA, because these methods increase the performance of read/write on those LUN.
Good luck

Re: Changes to multipath disks

Andrew Young_2 — Fri, 24 Apr 2009 10:09:56 GMT

Hi

Stephen I agree with the increasing disk sizes as I have been burned on HP-UX too, but there was always hope that it would work. But adding another LUN seems the best option.

Mohamed I am using the multipath drivers already, however since this is going to be for cvs and subversion performance is not an issue here.

I have also found this thread on adding LUNS with needing to reboot.
http://forums13.itrc.hp.com/service/forums/questionanswer.do?admit=109447627+1240569755262+28353475&threadId=1170635

Regards

Andrew Y

Re: Changes to multipath disks

Matti_Kurkela — Fri, 24 Apr 2009 10:15:57 GMT

Depending on the version of your HBA drivers, the new disks might be recognized automatically.

If they aren't, there are ways to make the driver recognize the new disks and/or forget the old ones without rebooting. Please see:

http://kbase.redhat.com/faq/docs/DOC-3942

MK