On 15-04-13 22:13, John Stoffel wrote:
"Roy" == Roy Sigurd Karlsbakk <roy@xxxxxxxxxxxxx> writes:
NOT a guess. Back up what you can, while you can, and start over. Use
"fdisk -u" so you can ensure partitions start on multiples of eight
(8)
sectors. (Modern fdisk uses 1MB alignment by default. Highly
recommended.)
So, if I start the partition at sector 64 (rather than 63), that's
better,
right (since 64 is a multiple of 8)? Or is there more math to do and
I'm still not getting it?
Roy> I still don't understand why people use partitions for RAID when
Roy> the whole drive is used anyway. Partitions were invented to
Roy> partition things up and are of no use if you want to spend the
Roy> whole drive's space for RAID use (or otherwise).
Because if I take a 2tb disk a I put a partition on there which is a
bit smaller than the full disk, if I then add a new 2tb (or any other
size) disk which says it's 2tb, but it's really a bit smaller, then
I'm not screwed. I've had it happen.
Or if you use them for your OS, and have several raids for /, /usr, /var
etc.
Or you buy 2 or 3 batches of disks, all varying sizes (1TB != 1TB) and
having partitions allows you to at least align them all to the same size.
And its even possible to buy a replacement disk, that's actually larger
but cheaper as prices came down.
A strange use case could be that 1 disk split into 2 partitions could be
a hot-spare for 2 arrays.
When using 1MiB offsets for partitions, I don't think there's any
performance loss at all (due to alignment) nor will it slow down
anything because md is on a partition rather then a disk. Wasting 1 MiB
per disk is really not significant.
And when using raid1/10 it allows you in theory to wipe the superblock
and make the partition point tot he real data; though there's very
little use for that imo.
I personally, don't see why you want to use the entire disk, is there
any advantage?
John
--
To unsubscribe from this list: send the line "unsubscribe linux-raid" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
--
To unsubscribe from this list: send the line "unsubscribe linux-raid" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
