On 03/25/2010 23:56, david@xxxxxxx wrote:
On Thu, 25 Mar 2010, Eric Sandeen wrote:
On Fri, 26 Mar 2010, Dave Chinner wrote:
Is there any reason for putting partitions on these block devices?
You could just use the block devices without partitions, and that
will avoid alignment potential problems....
I would like to raid to auto-assemble and I can't do that without
partitions, can I
I think you can.... it's not like MD is putting anything in the
table; you just give it block devices, I doubt it cares if it's a whole
disk or some partition.
Worth a check anyway ;)
I know that md will work on raw devices, but the auto-assembly stuff
looks for the right partition type, I would have to maintain a conf
file across potential system rebuilds if I used the raw partitions.
the next fun thing is figuring out what sort of stride, etc
should have used for this filesystem.
mkfs.xfs should suss that out for you automatically based on talking
of course you'd want to configure md to line up well with the hardware
in this case md thinks it's working with 10 12.8TB drives, I really
doubt that it's going to do the right thing.
I'm not exactly sure what the right thing is in this case. the
hardware raid is useing 64K chunks across 16 drives (so 14 * 64K worth
of data per stripe), but there are 10 of these stripes before you get
back to hitting the same drive again.
It does here at least, I never use partition tables on any of the arrays
here just use LVM against what it sees as the 'raw' disk. I haven't
tried it w/ a 128TB array but with smaller ones that's what I've used in
the past (hw raid, md raid-0, file system). Recently for systems now I
just use HW raid; LVM; and then filesystem (lvm does the striping/raid-0
function). when you create the physical volume w/ lvm just make sure
you allign it (older versions use --metadatasize to 'pad' the start
offset), newer versions have the dataalignment option.