Ooops, I needed to clarify something...
On Mon, Sep 17, 2012 at 06:26:12PM +0100, Andrew Haycock wrote:
<SNIP!>
> When Dan explained his setup, he brought to my attention his 64GB root
> disk. Aha! I think, this is something I was considering, but then I
> come away thoroughly confused as I try to understand what his 52GB
> rpool is used for (and indeed, what is rpool?), wonder at the 4GB
> swap/dump (when using Linux I deliberately move the swap to a
> mechanical drive to reduce wear on the SSD) and became utterly
> perplexed as to how a 4GB ZIL qualifies as over-provisioned on an SSD
> (I thought that ZIL was a log device and therefore written to a lot, I
> had considered buying a Gigabyte i-RAM from the States to server this
> role). Also Dan, do you use an L2ARC at all, could an SSD be
> worthwhile for this?
Okay, I made a mistake. 4GB isn't swap, just dump.
ZFS has two abstractions: The pool, and the filesystem.
A pool is comprised of one or more disk slices or one or more disks. Due to
the Illumos grub's inability to boot from EFI volumes, you must slice your
root disk into traditional Solaris/Illumos partitions.
My root ZFS pool is the 52GB partition on my ssd:
(1)# zpool status rpool
pool: rpool
<SNIP!>
config:
NAME STATE READ WRITE CKSUM
rpool ONLINE 0 0 0
c4t1d0s0 ONLINE 0 0 0
errors: No known data errors
(0)#
My data pool ("tank") is comprised of two whole 2TB disks, plus the 4GB slice
of SSD for slog:
(0)# zpool status tank
pool: tank
<SNIP!>
config:
NAME STATE READ WRITE CKSUM
tank ONLINE 0 0 0
mirror-0 ONLINE 0 0 0
c3t1d0 ONLINE 0 0 0
c5t3d0 ONLINE 0 0 0
logs
c4t1d0s4 ONLINE 0 0 0
errors: No known data errors
(0)#
On a pool is one or more filesystems. Let's look at rpool:
(1)# zfs list -r rpool
NAME USED AVAIL REFER MOUNTPOINT
<edited for content...>
rpool 15.4G 35.3G 45K /rpool
rpool/ROOT 10.6G 35.3G 31K legacy
rpool/ROOT/oi_151a4 9.75M 35.3G 9.28G /
rpool/ROOT/oi_151a6 10.6G 35.3G 9.34G /
rpool/local 440M 35.3G 440M /usr/local
rpool/zones 2.40G 35.3G 35K /zones
rpool/zones/nexenta 714M 35.3G 33K /zones/nexenta
rpool/zones/nexenta/ROOT 714M 35.3G 31K legacy
rpool/zones/nexenta/ROOT/zbe 714M 35.3G 714M legacy
rpool/zones/router 995M 35.3G 33K /zones/router
rpool/zones/router/ROOT 995M 35.3G 31K legacy
rpool/zones/router/ROOT/zbe-5 797K 35.3G 984M legacy
rpool/zones/router/ROOT/zbe-6 994M 35.3G 984M legacy
rpool/zones/webserver 744M 35.3G 33K /zones/webserver
rpool/zones/webserver/ROOT 744M 35.3G 31K legacy
rpool/zones/webserver/ROOT/zbe-5 971K 35.3G 734M legacy
rpool/zones/webserver/ROOT/zbe-6 743M 35.3G 734M legacy
(0)#
You create a filesystem on a pool, and then it gets mounted somewhere.
ZIL is written to a lot, but given my 2TB disks are 5900 RPM disks, even a
stock SSD is faster. I personally do not use L2ARC, given most of my home
server's filesystem usages is for backups, and at-most 35Mbit/sec web
connections will be more network bound than disk-bound anyway (assuming no
less than 10ms packet RTT, which is generous at a minimum).
> I did find the zones a little confusing too, but as I plan on setting
> up a virtual machine to practise on I'm sure I'll fathom things out
> soon enough.
Zones are lighter-weight VMs. You can give a zone its own TCP/IP stack,
which is what I do. They share kernels with other zones. Setup and teardown
of a zone is much quicker than a full-blown VM.
Hope this helps some more,
Dan
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