Current status of support for high end SAN hardware

Andy Kosela andy.kosela at
Mon Jun 9 12:41:25 UTC 2008

On Mon, Jun 9, 2008 at 12:36 PM, Russell Vincent <rv at> wrote:
> The FreeBSD support for multipath/SAN is fairly poor. It's fiddly
> to get to work and boot times are a little variable (into the
> minutes) as it tries to discover the devices.  Once it is configured
> and booted, it just works as long as things don't go wrong.  SAN
> outages cause the machine to hang up until the issue is resolved
> (in which case it just seems to continue) or it doesn't recover at
> all and requires a reboot.  Note that I don't spend a significant
> amount of time on this, so it may be that I could do things a little
> better.  I have also not tested the failover stuff very well (I
> only upgraded this machine to 7-STABLE fairly recently).  Disk
> access seems to be restricted to a single path at a time.  Problem
> solving is very tricky as there is very little information to trace
> which path/disk refers to which fabric/storage device/LUN.

Thank you for your insights. It's good to see you have no problems
with isp(4) and Qlogic HBAs. Though I'm concerned about
multipathing. We run 6.x-RELEASE releases so it seems we have
to upgrade to 7.0-RELEASE to achieve that goal. gmultipath(8)
code is fairly new so I suppose it's not that mature yet as in
Linux. Unfortunately it is only an active/passive approach with
no load balancing (the active path is active until a BIO request is
failed with EIO or ENXIO)

Good support for high end SAN environment is essential in
todays data centers, as most servers are connected to storage
using FC based storage area network. I hope things will improve
as 7.x-STABLE will be polished over time.

Mark, I completely agree with you that ZFS is much better than
Ext3+LVM2. Ext3 is still lacking internal snapshoting capability,
so it's even inferior to UFS2. As a matter of fact I'm watching
Oracle's btrfs development as it seems it will change many
things on Linux filesystems scene. Though I still fear ZFS on
FreeBSD is not as yet mature to the point of using it in a mission
critical 24x7 production environments. But it's definetly something
to watch out for.

Andy Kosela
ora et labora

More information about the freebsd-stable mailing list