Date: Fri, 4 Mar 2011 14:06:12 +0000 From: Dr Josef Karthauser <joe@tao.org.uk> To: Jeremy Chadwick <freebsd@jdc.parodius.com> Cc: Tom Evans <tevans.uk@googlemail.com>, freebsd-fs@freebsd.org Subject: Re: ZFS on a single disk? Message-ID: <C68871CF-AA8B-414F-B870-73AA378708BC@tao.org.uk> In-Reply-To: <20110304140015.GA27523@icarus.home.lan> References: <0E00DAFC-C39F-47DC-B9AF-16419C20997F@tao.org.uk> <615F1346-E830-42E2-B229-4181B8BC56BD@exonetric.com> <53FA69D2-2EF0-4CBF-985B-6E710F15FE02@tao.org.uk> <20110302001650.GB49147@icarus.home.lan> <27423168-85BE-41B1-8E14-94F01310EFE4@tao.org.uk> <20110302121612.GA61020@icarus.home.lan> <9EAE56CB-0CE9-4A08-B783-3EF9B1059E62@tao.org.uk> <AANLkTinp5-kHGePPtyiruxKVhWcioRrGwMAYe%2BygK76M@mail.gmail.com> <20110304131849.GA26774@icarus.home.lan> <0A0632A0-24C3-4B11-8542-37A58DCA6390@tao.org.uk> <20110304140015.GA27523@icarus.home.lan>
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On 4 Mar 2011, at 14:00, Jeremy Chadwick wrote: > On Fri, Mar 04, 2011 at 01:49:15PM +0000, Dr Josef Karthauser wrote: >> I don't believe that that's an issue anymore. The XEN kernel comes >> configured with PAE as a default option, and I've seen elsewhere that >> there is no technical problems running ZFS in a PAE environment. (The >> PAE docs are out of date when they say we can't use kernel modules, >> and any 64 bit aware kernel model should run with PAE with no >> difficulties). > > XEN isn't something I'm familiar with, which is obviously a huge part of > the problem with me trying to give you advice on the matter. :-) The > only virtualisation "system" I'm familiar with is VMware Workstation, > which isn't anything like XEN. > > What I'm going off of is /sys/i386/conf/PAE vs. /sys/i386/conf/XEN. > > Be sure to notice all the "nodevice" lines in /sys/i386/conf/PAE, and > the comment directly above those. The XEN configuration file has > "options PAE", which is ultimately what a driver/piece of kernel code > would use for compile-time detection for supporting/working under PAE. > > For example, arcmsr(4) will flat out panic() (intentionally) if PAE > is used. bge(4) and twa(4) appear to have a 4GB boundary on DMA; I > don't know the implications of this. Luckily I care not about device support. As long as the paravirtualised devices work, and zfs works, I need nothing else. So, I guess the zfs question boils down to whether (given everything else being equal with PAE support) I could consider zfs on i386 with a PAE memory model to be stable enough for a production server (on 8.2). Joe
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