[NCLUG] Installing ubuntu 12.04 to ZFS root directory

[Zak Smith]

My zfs pools run at approximately the expected speeds, on fast
machines using debian 6.  Make sure dedup and compression are off
unless you really for sure have them on for a good reason and have the
right resources to make them work.  Although throughput is where I
expect it, filesystem operation latency during some loads is extremely
poor (ie, a zpool status taking minutes or more during a big write or
pool scrub).

The boot order thing is screwed up and probably has to do with how
your bios is trying to locate boot sectors, etc, and has nothing per
se to do with zfs.

Personally I will not use linux/md raid again unless it is solely for
transient data and I need the raw speed in a raid0.  I would prefer to
use systematic ad hoc redundancy over two disks rather than a linux
raid to recover after a fault.





On Mon, Aug 19, 2013 at 01:43:19PM -0600, Phil Marsh wrote:
> Hi,
> I had a question for those who tried ZFS. I am running ZFS RAIDZ2 with four 1TB drives, two are Seagate Barracudas and two are WD blacks. I am booting (MBR + /boot/grub from an older 500GB WD black and otherwise have the rest of the / and /home directories on a ZFS RAIDZ2 pool. My machine has 8GB 800MHz DDR2 RAM and an older quad core Intel (I think 6400 from 2007). The transfer rate of my SATA controllers is, I think, rated at 3GB/sec. The OS is Ubuntu 12.04 (64B)
> My issue is that I'm noticing my booting is taking about 3x longer than my old Ubuntu 10.04 configuration (booted from a single drive with RAID 5 MDADM) and the machine winds up trying to access the floppy even though it's disabled for boot in the BIOS.
> Software installation seems to be slow too.
> Moreover, a check on iostat shows read BW of ~300K and write BW of about 3.5M. That seems slow to me.
> I'm beginning to wonder if I should just go to MDADM (software) RAID6 for my /home?
> Could someone kindly comment? Any suggestions and what is your experience with ZFS? Am I crazy to be using RAIDZ2 with four disks and the / directory for the most part, in the RAIDZ2?
> Thanks,

--
# Zak Smith    mobile 970-232-4468