Date: Fri, 19 Apr 2013 09:59:11 -0600 From: Scott Long <scott4long@yahoo.com> To: "Desai, Kashyap" <Kashyap.Desai@lsi.com> Cc: freebsd-scsi@freebsd.org Subject: Re: New Driver for MegaRaid 6Gb/s and 12Gb/s Card Message-ID: <B5195BC9-0E44-4D69-AC25-EE2EC4035B4D@yahoo.com> In-Reply-To: <B2FD678A64EAAD45B089B123FDFC3ED760761F4FB0@inbmail01.lsi.com> References: <B2FD678A64EAAD45B089B123FDFC3ED75E70AC49E1@inbmail01.lsi.com> <1366236517.1499.31.camel@localhost> <B2FD678A64EAAD45B089B123FDFC3ED760761F4E25@inbmail01.lsi.com> <516FF87E.8030702@freebsd.org> <B2FD678A64EAAD45B089B123FDFC3ED760761F4FB0@inbmail01.lsi.com>
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On Apr 19, 2013, at 12:44 AM, "Desai, Kashyap" <Kashyap.Desai@lsi.com> = wrote: >=20 >=20 >> -----Original Message----- >> From: owner-freebsd-scsi@freebsd.org [mailto:owner-freebsd- >> scsi@freebsd.org] On Behalf Of Matthew Jacob >> Sent: Thursday, April 18, 2013 7:13 PM >> To: freebsd-scsi@freebsd.org >> Subject: Re: New Driver for MegaRaid 6Gb/s and 12Gb/s Card >>=20 >> On 4/17/2013 11:25 PM, Desai, Kashyap wrote: >>> Hope my response clarifies your doubts. ~ Kashyap >> No, it doesn't. >>=20 >> What will happen if mrsas and mfi are both compiled into the kernel = and >> it boots on a system with the 1st thunderbolt? >>=20 >> It would be best to have one driver for the same hardware, period. >=20 > We are planning to move mfi and mrsas as loadable kernel module, once = mrsas driver is submitted. With this, we will provide device.hint = tunable option for customer to load mfi vs mrsas for Thunderbolt card. > Best solution is not to have two drivers works with same hardware, but = due to development cycle LSI added immediate support for > Thunderbolt card in current mfi driver. Now we have new driver = developed for the same card "mrsas". >=20 > Customer also wanted to provide choice between mfi vs mrsas for = Thunderbolt card until they found "mrsas" is working fine without any = major issue for them. > LSI decided based on customer request and they did not wanted to force = customers to use "mrsas" driver as immediate effect. There may be some = customer who are using "mfi" driver in production environment and do not = want to switch to "mrsas" if they upgrade FeeBSD kernel. >=20 > This provision of mfi vs mrsas priority is only temporary and in = future, we should plan to remove Thunderbolt (Device ID 0x005B) from mfi = because LSI will continue new development on "mrsas" What will the exposed device names of the arrays be under the new = driver? Will it still be /dev/mfid* ? If it's not, then this is where = the problem lies. Many users still use device names in their /etc/fstab = for mounting all of their filesystems at boot. If you have two drivers = that will compete for the same hardware and give that hardware different = names, they will break the fstab files for those users and they upgrade = over time. A similar situation occurred several years ago with the = Intel e1000 driver; it was split into two drivers, with certain hardware = that was supported by the old hardware going to the new driver. That = broke the network configuration for many users and caused years of pain = and unhappiness as users upgraded and were hit by the switch. We don't = want that to happen here. The real solution is that we need to have a single common naming = convention for all disks (and for network interfaces), and leave the = details of individual driver names out of the configuration part of the = system. That's not likely to happen any time soon. The other solution = is to mandate that users use volume labels for mounting their = filesystems, but that's not likely to happen either, and even if it did, = it present challenges for migrating existing users. The only remaining = solution that I can think of is to have the mfi and mrsas drivers share = the same devclass for their disk interfaces (mfid*), but that's a hack = that has not been fully explored in FreeBSD. Still, I'd encourage you = to try it and see if you can make it work. If you have any problems, = email me directly. Scott
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