partitioning a RAID 0 drive

[Tom H]

On Mon, Sep 6, 2010 at 10:41 AM, Liam Proven <lproven at gmail.com> wrote:
> On 6 September 2010 15:10, Tom H <tomh0665 at gmail.com> wrote:
>> On Mon, Sep 6, 2010 at 6:59 AM, Liam Proven <lproven at gmail.com> wrote:
>>> On 6 September 2010 02:33, Roy Lowrance <roy.lowrance at gmail.com> wrote:
>>>> I'd like to install Ubuntu on my Windows 7 PC and dual boot.
>>>>
>>>> The PC has a RAID 0 card and I see one device and three subdevices in the
>>>> Ubunut "Prepare partitions" dialogue:
>>>> /dev/mapper/isw_dgijegbagg_RAIDVOL
>>>>    /dev/mapper/isw_dgijegbaff_RAIDVOL1 type=ntfs, size =104MB
>>>>    /dev/mapper/isw_dgijegbaff_RAIDVOL2 type=ntfs, size=1987802 MB
>>>>    /dev/mapper/isw_ghijegbaff_RAIDVOL3 type=ntfs, size = 12485MB
>>>>
>>>> What I'd like to do is to split the 2 subdevice, the one with almost 2 GB of
>>>> storage.
>>>>
>>>> I may also need a swap partition.
>>>>
>>>> How should I proceed?
>>>
>>> Don't.
>>>
>>> Dual-booting off a RAID is somewhere between "extremely difficult and
>>> very dangerous" and "flat-out impossible".
>>
>> ???!!!
>>
>> Judging from the name of the raid partitions, this is fakeraid.
>
> Exactly.
>
>> If
>> Ubuntu couldn't boot/dual-boot from it, there'd be a whole range of
>> desktops on which Ubuntu couldn't be installed.
>
> Beware. There is a *huge* difference between booting - which isn't a
> problem - and dual-booting, which is a totally different kettle of
> fish. You are conflating the 2.

I meant both boot and dual-boot. Whether conflating or not, if Windows
is using fakeraid, Ubuntu has to use it too; it is possible, although
I have admittedly only done it once.


>> I don't know the graphical installer that well but If you select
>> raidvol2, don't you get an option to install Ubuntu alongside Windows?
>
> The 2 OSs use totally different methods to create and manage RAID
> arrays. If things go 1 sector out of perfect sync, I would expect one
> OS to instantly trample all over the other's data.

All Linux distributions would have a "DON'T DUAL-BOOT WITH FAKERAID"
warning at install time if fakeraid (or biosraid as it it sometimes
more accurately called) were that fragile. Anyway, the partitions are
set up by the BIOS and are managed by, on the Linux side, dmraid so
there cannot be any trampling.


>> Also, it's 2 TB not 2 GB.
>
> I didn't even get that far, but I did wonder about sharing 2GB of disk
> between 2 21st-century OSs!

That was for the OP not you. In fact, when I first read Roy's email, I
wondered how anyone could fit Win7 and Ubuntu on 2 GB. The smallest
default Ubuntu server install just about fits on 2 GB partition...