On 10/13/12 22:13, Jim Klimov wrote:
2012-10-13 0:41, Ian Collins пишет:
On 10/13/12 02:12, Edward Ned Harvey
(opensolarisisdeadlongliveopensolaris) wrote:
There are at least a couple of solid reasons *in favor* of partitioning.
#1 It seems common, at least to me, that I'll build a server with
let's say, 12 disk slots, and we'll be using 2T disks or something
like that. The OS itself only takes like 30G which means if I don't
partition, I'm wasting 1.99T on each of the first two disks. As a
result, when installing the OS, I always partition rpool down to ~80G
or 100G, and I will always add the second partitions of the first
disks to the main data pool.
How do you provision a spare in that situation?
Technically - you can layout the spare disks similarly and attach
the partitions or slices as spares for pools.
I probably didn't didn't make my self clear, so I'll try again!
Assuming the intention is to get the most storage from your drives. If
you add the remainder of the space on the drives you have partitioned
for the root pool to the main pool giving a mix of device sizes in the
pool, how do you provision a spare?
That's why I have never done this. I use whole drives everywhere and as
you mention further down, use the spare space in the root pool for
scratch filesystems.
However, in servers I've seen there were predominantly different
layout designs:
1) Dedicated root disks/mirrors - small enough for rpool/swap
tasks, nowadays perhaps SSDs or CF cards - especially if care
was taken to use the rpool device mostly for reads and place
all writes like swap and logs onto other pools;
2) For smaller machines with 2 or 4 disks, a partition (slice)
is made for rpool sized about 10-20Gb, and the rest is for
data pool vdevs. In case of 4-disk machines, the rpool can be
a two-way mirror and the other couple of disks can host swap
and/or dump in an SVM or ZFS mirror for example. The data pool
components are identically sized and form a mirror, raid10 or
a raidz1; rarely a raidz2 - that is assumed to have better
resilience to loss of ANY two disks than a raid10 resilient
to loss of CORRECT two disks (from different mirrors).
3) For todays computers with all disks being big, I'd also
make a smallish rpool, a large data pool on separate disks,
and use the extra space on the disks with rpool for something
else - be it swap in SVM-mirrored partition, a scratch pool
for incoming data or tests, etc.
Most of the system I have built up this year are 2U boxes with 8 to 12
(2TB) drives. I expect these are very common at the moment. I use your
third option but I tend to just create a big rpool mirror and add a
scratch filesystem rather than partitioning the drives.
--
Ian.
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