Re: [PLUG] SAN Questions

On 5/31/07, Stephen Gran <steve@lobefin.net> wrote:

On Thu, May 31, 2007 at 03:54:08PM -0400, Jeff McAdams said:
> Sean Cummins wrote:
>
> > - You'll need the HBA drivers themselves, HBA firmware, management
> > utilities (eg. SANSurfer or HBAnyware), array management host software
> > (eg., Solutions Enabler, Navisphere), and multipath software (eg.,
> > Powerpath).
>
> <opinion type=personal>Just say "NO" to proprietary multipathing
> software.</opinion>
>
> Linux mainstream kernels, and thus most of the modern distros support
> standard (Linux device mapper multipathing), and standard'ish (Qlogic
> driver level multipathing) capabilities for multipathing.
>
> Our experience was with HP SecurePath and HP EVA's, and we had *severe*
> problems with SecurePath.  When we converted over to Qlogic's
> multipathing capabilities, *all* of our issues with multi-pathing went
> away (to HP's credit, this is the direction they're going for their
> support of Linux).  I would like to move to device mapper based
> multi-pathing, but we haven't done the engineering work yet to try that
> out and make that happen.

I helped a friend of mine set up standard in-kernel based multipathing
at his workplace, and it works great.  We could pull one cable out of
the switch, and processes hung for a few seconds in I/O wait, and then
continued on using the other path.

> > - The HBA drivers are supported by the HBA manufacturers and EMC.
> > - Powerpath has essentially the same look, feel, and functionality on
> > Linux as Solaris/HPUX/AIX.  VMware ESX has its own multipathing built
> > in.
> > - I'm not aware of any hot-swappable HBA support on Linux.
>
> I have no personal experience on this last point either.  I'm not sure
> how well Linux PCI support handles hot-swap PCI in general, HBA's would
> essentially be a special case of that.

Hot swap PCI support is nearly there - the real work now is to make the
drivers that support hot swappable pci devices periodically rescan the
buses themselves, as many scsi and usb drivers already do.  For some
drivers, I think the work is at least underway.
--
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|  Stephen Gran                  | A wife lasts only for the length of the |
|   steve@lobefin.net             | marriage, but an ex-wife is there *for  |
|  http://www.lobefin.net/~steve | the rest of your life*.   -- Jim        |
|                                | Samuels                                 |
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