Cc: "Discussion list for Red Hat Enterprise Linux 4 \(Nahant\) Beta" <nahant-beta-list redhat com>
Subject: Re: IBM's RDAC drvier for multipath support.
Date: Wed, 24 Nov 2004 16:28:22 -0800 (PST)
Now that RedHat has decided mdadm full disk multipath will not be
supported in RHEL4,
You can find more info in: RedHat Service Request No. 362830
I have been told using mdadm to provide full multipath disk
redundancy is not recommended or supported in RHEL3 or the up coming
RHEL4. That technically it "may" function if installed via kickstart. I
assume by having %post ext2resizes the partitions, then assemble them as
md devices, change /etc/fstab etc.. etc... However my testing of RHEL3
and RHEL4B1 suggests anaconda still has problems with partitioning and/or
installation when two active paths are available. So I fail to see how
kickstart %post would be successful building mdadm multipath devices.
This is of course is ignoring how overly complex and unsupportable this
configuration would be and the unanswered question if grub and/or initrd
even support booting a multipathed device.
I have had nothing but great experiences with RedHat in the past and am
amazed something as basic and fundamental as multipathed disks
is so very lacking in this day and age of SANs and Blade servers.
Compared to the above mess RDAC is simple and straight forward (from the
customers stand point anyways). The main issue here is that a) RedHat
does not support it and b) Every time RedHat updates their kernel we have
to rebuild RDAC modules (which isn't as easy as it sounds).
"Given enough time, all legal battles in the tech industry will invoke the
DMCA. This generally means that all constructive arguments have ended."