zfs discuss - Sep 2010 - Please warn a home user against OpenSolaris under VirtualBox under WinXP ; )

Pardon in advance my n00b ignorance. (Yes I have googled a [i]lot[/i] before
asking.)

I am considering VirtualBoxing away one physical machine at home, and running
WinXP as host (yes, as atrocious it may seem, explanation below [1]) and
OpenSolaris guest as file server, with OpenSolaris (why?[2]) having raw access
to all my SATA drives. (OSes on the IDE channel). This is for home use, as a
media center -- files basically written 4 TB once and for all and later only
rare addtions or overwrites.

If this is a bad idea, I''d like to be warned before I spend another two
weeks trying to learn, reinstall (initial bare-metal testing OK), swear &
curse, populate and swear & curse.

* Raw access. 
- ZFS is best off accessing physical devices, right? That means raw access, or
is that even insufficient?
- I am a bit scared at Windows having access to the critical hard drives ;)  And
raw access is considered "for experts", which I ain''t. And
there are concerns like flush drive ( comments in
http://blogs.sun.com/mock/entry/stupid_virtualbox_zfs_tricks ) -- solvable yes,
but I am not confident I know all the warnings.
- FTR, I will anyway have a few-months-old backup at work, so I am not too
worried at a sudden data loss due to my own screwing up.

* Memory. 
- As said, hardly any write operations, so OpenSolaris seems to run perfectly
well on this (bare metal) with even less than 1GB under "no load", but
I haven''t even tried to populate with data -- how much to even idle on
a 5TB RAID-Z?
- This mobo clocks down RAM if using more than 2 slots.


[1] Why XP as _host_? 
- Will sometimes run XP on bare metal for performance -- I can then simply pause
the VM.
- Running my pre-installed XP under VirtualBox looks like a nightmare, judging
from some googling
- Stability? If XP crashes, I don''t need to access my media files until
XP is up and running again. Would of course be quicker to restart in VM, but
hey, server uptime is really not an issue.
(- Better network card support.)
- I might have an OpenSolaris installation running on bare metal for those
occational heavier tasks, and stick to my laptop for those couple of days.

[2] Why OpenSolaris at all?
- Would like ZFS for RAID management (5 disk RAID-Z) and snapshotting (basically
[i]every[/i] time a file is overwritten!).
-- 
This message posted from opensolaris.org

I have another question to add to the two you already asked and answered.

Why not two separate machines, one for XP, one for zfs/raid?  At
today''s network speeds, hooking a cable between those two would provide
any speed data access to the files in the raid that you want. A suitable ZFS
machine could sit in another room if you want the quiet for home theater.

The idea of having one set of hardware run everything is clever, and
virtualizing everything is neat, efficient - and complicated.

Now that Oracle has gutted Open Solaris, I''m forced to once again
articulate why I got into Open Solaris about a year ago - I wanted ZFS, and was
willing to go learn Open Solaris to get it. ZFS was a powerful motivator. But I
can get what I need there with just a ZFS back end machine; and last-generation
hardware is very, very cheap. For me, the UN complication of using two hardware
setups is well worth it.
-- 
This message posted from opensolaris.org

There was a guy doing that: Windows as host and OpenSolaris as guest with raw
access to his disks. He lost his 12 TB data. It turned out that VirtualBox dont
honor the write flush flag (or something similar).

In other words, I would never ever do that. Your data is safer with Windows only
and a Windows raid solution.

Use OpenSolaris as host instead, and Win as guest.
-- 
This message posted from opensolaris.org

On Wed, Sep 22, 2010 at 07:14:43AM -0700, Orvar Korvar
wrote:
> There was a guy doing that: Windows as host and OpenSolaris as guest
> with raw access to his disks. He lost his 12 TB data. It turned out
> that VirtualBox dont honor the write flush flag (or something
> similar).
VirtualBox has an option to honor flushes.

Also, recent versions of ZFS can recover by throwing out the last N
transactions that were not committed fully.
> In other words, I would never ever do that. Your data is safer with
> Windows only and a Windows raid solution.
> 
> Use OpenSolaris as host instead, and Win as guest.
I don''t think your advice is correct.  If you''re going to run
production
services on VirtualBox VMs then you should enable cache flushes in VBox:

http://www.virtualbox.org/manual/ch12.html#id2692517

"
To enable flushing for IDE disks, issue the following command:

VBoxManage setextradata "VM name"
      "VBoxInternal/Devices/piix3ide/0/LUN#[x]/Config/IgnoreFlush" 0

The value [x] that selects the disk is 0 for the master device on the
first channel, 1 for the slave device on the first channel, 2 for the
master device on the second channel or 3 for the master device on the
second channel.

To enable flushing for SATA disks, issue the following command:

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

The value [x] that selects the disk can be a value between 0 and 29.
"

IMO VBox should have a simple toggle for this in either its disk or vm
manager UI.  And the flush commands should be honored by default.  What
VBox could do is have some radio buttons or checkboxes for indicating
the purpose of a given VM, and then derive default flush behavior from
that (e.g., test and gaming VMs need not honor flushes, dev VMs might,
and prod VMs do).

Nico
--

@ kebabber:
> There was a guy doing that: Windows as host and
> OpenSolaris as guest with raw access to his disks. He
> lost his 12 TB data. It turned out that VirtualBox
> dont honor the write flush flag (or something
> similar).
That story is in the link I provided, and as has been pointed out here, it is
solvable.

I am more worried that the hard drives I wanted to reserve for server use, will
be taken over by host. "Initialized" in MS''esque, might be
dangerous?
-- 
This message posted from opensolaris.org

Hmm...according to
http://www.mail-archive.com/vbox-users-community at
lists.sourceforge.net/msg00640.html

that''s only needed before VirtualBox 3.2, or for IDE.  >= 3.2,
non-IDE should
honor flush requests, if I read that correctly.

Which is good, because I haven''t seen an example of how to enabling
flushing
for SAS (which is the emulation I usually use because it''s supposed to
have
better performance).
-- 
This message posted from opensolaris.org

OK, replying to myself after having played around a bit with both Unix under
Billware and vice versa:

1) 
- Somehow the HDs turned into a "GPT Protective Partition", which XP
cannot read. Googling a bit reveals that XP cannot read these (although a
utility for destroying and reformatting is available).

XP not touching it is A Good Thing I think. Sorry for letting this slip into a
Billware support question, but:
----> Is it safe to have a guest OS raw-accessing these discs, without
worrying that the data being destroyed by an XP host?


2) 
- Using XP under OpenSolaris (build 134, most recent VirtualBox) is still not
appealing -- even having done a fresh install. It is unbearably slow, I
can''t even play a media file on an external USB soundcard (using
pass-through).



So ... either WinXP host, or another box.
-- 
This message posted from opensolaris.org

At the risk of being repetitive:

[i]Why not two separate machines, one for XP, one for zfs/raid?[/i] At
today''s network speeds, hooking a cable between those two would provide
any speed data access to the files in the raid that you want. A suitable ZFS
machine could sit in another room if you want the quiet for home theater.

The idea of having one set of hardware run everything is clever, and
virtualizing everything is neat, efficient - and [i]complicated[/i].

Now that Oracle has gutted Open Solaris, I''m forced to once again
articulate why I got into Open Solaris about a year ago - I wanted ZFS, and was
willing to go learn Open Solaris to get it. ZFS was a powerful motivator. But I
can get what I need there with just a ZFS back end machine; and last-generation
hardware is very, very cheap. [i]For me, the UN complication of using two
hardware setups is well worth it.[/i]
-- 
This message posted from opensolaris.org

Well at the risk of being repetetive too: 
"or another box".

So yes I am considering it, but that is probably the option that requires less
guidance in this thread.
-- 
This message posted from opensolaris.org