On 04/ 3/10 10:23 AM, Edward Ned Harvey wrote:
Momentarily, I will begin scouring the omniscient interweb for
information, but I’d like to know a little bit of what people would
say here. The question is to slice, or not to slice, disks before
using them in a zpool.
Not.
One reason to slice comes from recent personal experience. One disk of
a mirror dies. Replaced under contract with an identical disk. Same
model number, same firmware. Yet when it’s plugged into the system,
for an unknown reason, it appears 0.001 Gb smaller than the old disk,
and therefore unable to attach and un-degrade the mirror. It seems
logical this problem could have been avoided if the device added to
the pool originally had been a slice somewhat smaller than the whole
physical device. Say, a slice of 28G out of the 29G physical disk.
Because later when I get the infinitesimally smaller disk, I can
always slice 28G out of it to use as the mirror device.
What build were you running? The should have been addressed by CR6844090
that went into build 117.
There is some question about performance. Is there any additional
overhead caused by using a slice instead of the whole physical device?
There is another question about performance. One of my colleagues said
he saw some literature on the internet somewhere, saying ZFS behaves
differently for slices than it does on physical devices, because it
doesn’t assume it has exclusive access to that physical device, and
therefore caches or buffers differently … or something like that.
it's well documented. ZFS won't attempt to enable the drive's cache
unless it has the physical device. See
http://www.solarisinternals.com/wiki/index.php/ZFS_Best_Practices_Guide#Storage_Pools
--
Ian.
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