Date: Sat, 11 Oct 2008 15:28:01 +0200 From: Danny Braniss <danny@cs.huji.ac.il> To: Jeremy Chadwick <koitsu@FreeBSD.org> Cc: freebsd-hackers@freebsd.org, Mike Meyer <mwm-keyword-freebsdhackers2.e313df@mired.org> Subject: ZFS boot Message-ID: <E1KoeVm-000ELP-4b@cs1.cs.huji.ac.il>
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> > > > so can Freebsd boot off a ZFS root? in stable? current? ... > > > > > > boot0 doesn't apply here; it cares about what's at sector 0 on the > > > disk, not filesystems. > > > > > > boot2/loader does not speak ZFS -- this is why you need the /boot UFS2 > > > partition. This is an annoyance. > > > > > > For the final "stage/step", vfs.root.mountfrom="zfs:mypool/root" in > > > loader.conf will cause FreeBSD to mount the root filesystem from ZFS. > > > This works fine. > > > > so the answer is: > > yes, if you have only one disk. > > no, if you have ZFS over many disks > > > > because I see no advantage in the springboard solution where ZFS is used to > > cover several disks. > > > > I'm asking, because I want to deploy some zfs fileservers soon, and so > > far the solution is either PXE boot, or keep one disk UFS (or boot off a USB) > > Today's /(root+usr) is somewhere between .5 to 1Gb(kernel+debug+src), > > and is readonly, so having 1 disk UFS seems to be a pitty. > > Hold on a minute. "One disk" has nothing to do with the filesystem. > You asked if FreeBSD could boot off of a specific filesystem, and I > answered that -- I didn't state anything about disk counts. Now you're > changing the focus. :-) > not intentionaly, but once you mention boot0/2, bsdlabel, slice/partition ... /OT Initially, I was not thrilled with ZFS, but once you cross the few hundred gigabyte filesystems UFS is impractical, and though old sysadmins will have to be re-educated (zfs catch-all-commands, instead of mount/fsck/export/blah...) it is the (only?) way for the new-terrabyte-world. So having bitten the bullet, and doing some experiments i'm stuck as to what to do with / OT/ > I'm pretty sure FreeBSD can boot off of gmirror setups (see above, > boot2/loader should work off of gmirror), which means >1 disk. You > do not have to gmirror the entire disk, you can gmirror just a slice > (AFAIK). but gmirror is not ZFS, and yes it can, why not. > > I think (hope?) you can use the "remaining" (e.g. non-UFS/non-gmirror) > part of the 2nd disk for ZFS as well, otherwise the space would go > to waste. The "Root on ZFS configuration" FreeBSD ZFS Wiki page > seems to imply you can. The idea is to used the 'free/remaining' as part of the BIG ZFS 'array' [ED note : I've highjacked the 'Re: continuous backup solution for FreeBSD'] To Matt: since 'small' nowadays is big enough to hold /, what advantages are there in having root split up? also, having this split personality, what if the disk goes? the hammer/zfs is probably raided ... [btw, having a small-boot-partition brings back bad memories: the first thing I did on a new Compact was boot it diskless, repartition the disk, newfs, and I could no longer boot it :-) - part of the BIOS was there] To Doug: > ZFS boot is coming. great! any time estimate?, just curious, no preasure :-) some food for thought: In the past raid 5 would reduce the throughput conciderably, though nowadays it's hardly notisable, so I guess my reluctance to having a swap partition raided is gone. danny
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