zfs discuss - Jan 2011 - ZFS advice for laptop

Hi All,

I have a laptop with twin 500 GB hard disks and I''m looking how best to
protect my data.  I would run Open Solaris as my primary system however I have
specific hardware requirements which means I am forced to use Windows 7 as my
primary o/s.  However I would like to utilise the power of ZFS manage my data
needs.

Currently I am experimenting with the following set-up:

1) Create 2 RAW partitions in Windows 7 on each physical disk of 350 GB,
remember 1 disk will have Windows 7 NTFS partitions, and I might install a Linux
host on the other disk meaning a few EXT4 partitions
2) Create VirtualBox Open Solaris guest on a 10 GB vdi disk
3) Give the guest VM raw disk access to the 2 partitions created in step 1 and
attach using VirtualBox SATA controller, a VMDK container file is created to
represent each partition
4) Make VirtualBox honour flushing by issuing the following command for the two
partitions:

VBoxManage setextradata "VM name"
"VBoxInternal/Devices/ahci/0/LUN#[x]/Config/IgnoreFlush" 0

5) In Open Solaris create a mirrored pool using the two partitions and make it a
SMB share
6) Mount share in Windows 7 host

Now the above has worked a treat so far, but I am yet to test by pulling the
plug on the VM during read and write operations etc, but the reason for posting
is that the official documentation recommends NOT using partitions on disks and
using whole physical disks is encouraged.

What I would like to know is what risks do I carry by using partitions, I
attempted to search for the rationale behind this advice but I can''t
seem to find it...

If the implications are serious and the likelihood of them occurring then I have
thought of using one the internal physical 500 GB disks coupled with an external
USB 500 GB disk that I have, in which case at times the pool would operate in a
degraded state as the USB drive will not always be connected, in which case
re-silvering would take place to sync the mirror, again any serious implications
of doing this??

Many Thanks,

Jana
-- 
This message posted from opensolaris.org

On Mon, 3 Jan 2011, Jana Mann wrote:
>
> What I would like to know is what risks do I carry by using 
> partitions, I attempted to search for the rationale behind this 
> advice but I can''t seem to find it...
As far as I am aware, there is no additional risk from using 
partitions except that there are a few drawbacks.  Zfs will disable 
write caching if it sees that a partition is being used and this will 
lose some performance.  Since a partition lives with other partitions 
on the same disk, if something goes wrong with one of the partitions, 
then the administrative work to repair is greatly magnified.  It is 
much easier to just be able to slam in a different disk.

Bob
-- 
Bob Friesenhahn
bfriesen at simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/

On 01/04/11 18:40, Bob Friesenhahn wrote:
> Zfs will disable write caching if it sees that a partition is being used
This is backwards.

ZFS will enable write caching on a disk if a single pool believes it 
owns the whole disk.

Otherwise, it will do nothing to caching.  You can enable it yourself 
with the format command and ZFS won''t disable it.

					- Bill