On 13/01/18 22:40, Dave Chinner wrote: > On Sat, Jan 13, 2018 at 07:29:19PM +0000, Wol's lists wrote: >> On 13/01/18 00:20, Stan Hoeppner wrote: >>> It's not set in stone. If the RAID geometry changes one can >>> specify the new geometry at mount say in fstab. New writes to the >>> filesystem will obey the new specified geometry. > > FWIW, I've been assuming in everything I've said that an admin > would use these mount options to ensure new data writes were > properly aligned after a reshape. > >> Does this then update the defaults, or do you need to specify the >> new geometry every mount? Inquiring minds need to know :-) > > If you're going to document it, then you should observe it's > behaviour yourself, right? You don't even need a MD/RAID device to > test it - just set su/sw manually on the mkfs command line, then > see what happens when you try to change them on subsequent mounts. I suppose I could set up a VM ... > > Anyway, start by reading Documentation/filesystems/xfs.txt or 'man 5 > xfs' where the mount options are documented. That's answer most FAQs > on this subject. > > "Typically the only time these mount options are necessary > if after an underlying RAID device has had it's geometry > modified, such as adding a new disk to a RAID5 lun and > reshaping it." anthony@ashdown /usr/src $ man 5 xfs No entry for xfs in section 5 of the manual anthony@ashdown /usr/src $ > > It should be pretty obvious from this that we know that people > reshape arrays and that we've have had the means to support it all > along. Despite this, we still don't recommend people administer > their RAID-based XFS storage in this manner.... > Note I described myself as *editor* of the raid wiki. Yes I'd love to play around with all this stuff, but I don't have the hardware, and my nice new system I was planning to do all this sort of stuff on won't POST. I've had that problem before, it's finding time to debug a new system in the face of family demands... and at present I don't have an xfs partition anywhere. Reading xfs.txt doesn't seem to answer the question, though. It sounds like it doesn't update the underlying defaults so it's required every mount (which is a safe assumption to make), but it could easily be read the other way, too. Thanks. I'll document it to the level I understand, make a mental note to go back and improve it (I try and do that all the time :-), and then when my new system is up and running, I'll be playing with that to see how things behave. Cheers, Wol -- To unsubscribe from this list: send the line "unsubscribe linux-xfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
