Doing RAID0 dangerous ?

I just got a new Motherboard with inbuilt RAID0 capabilities over a
pair of serial ATA hard disks.
1. I was wondering if I will be able to take this pair of hard disks to
another motherboard in the future and still be able to see all the data
it has intact ( somebody told me that the motherboard supported RAID is
specific to motherboard and that I will lose all the data if I change
the motherboard )

2. How does the hardware raid compare with Linux raid support in terms
of speed ?
3. If I do a hardware RAID now, will I be able to move it to a computer
without RAID support but running Linux RAID

Thanks
--sony

(E-Mail Removed) wrote:

> I just got a new Motherboard with inbuilt RAID0 capabilities over a
> pair of serial ATA hard disks.
> 1. I was wondering if I will be able to take this pair of hard disks to
> another motherboard in the future and still be able to see all the data
> it has intact ( somebody told me that the motherboard supported RAID is
> specific to motherboard and that I will lose all the data if I change
> the motherboard )

That depends. When you set up a RAID-0 array you will be asked for the block
size to use. If you move the hard drives to another MB and use the same block
size then PROBABLY it will work as long as the new MB sees the EXACT same HD
geometry as the old one.

> 2. How does the hardware raid compare with Linux raid support in terms
> of speed ?

It does not compare! It is WAY faster than software RAID.

> 3. If I do a hardware RAID now, will I be able to move it to a computer
> without RAID support but running Linux RAID

I do not know the answer to that one.

> Thanks
> --sony

--
Phil Frisbie, Jr.
Hawk Software
http://www.hawksoft.com

On Fri, 17 Jun 2005 21:56:45 GMT, Phil Frisbie, Jr. wrote:
> (E-Mail Removed) wrote:
>
> > I just got a new Motherboard with inbuilt RAID0 capabilities over a
> > pair of serial ATA hard disks.
> > 1. I was wondering if I will be able to take this pair of hard disks to
> > another motherboard in the future and still be able to see all the data
> > it has intact ( somebody told me that the motherboard supported RAID is
> > specific to motherboard and that I will lose all the data if I change
> > the motherboard )
>
> That depends. When you set up a RAID-0 array you will be asked for the block
> size to use. If you move the hard drives to another MB and use the same block
> size then PROBABLY it will work as long as the new MB sees the EXACT same HD
> geometry as the old one.

There's an overhead in the data which lives on the disk, and a
lot of raid controllers do that overhead differently. Getting
that to work between two different controllers is less probable
than what you wrote seems to indicate.

In short, likely to be problematic. Also note that a lot of SATA
raid controllers are really software raid controllers, where the
software lives in BIOS - more info on
http://linux.yyz.us/sata/faq-sata-raid.html

> > 2. How does the hardware raid compare with Linux raid support in terms
> > of speed ?
>
> It does not compare! It is WAY faster than software RAID.

In all cases? You'll really need to substantiate that. Most of
the cheaper raid cards and integrated controllers are software
raids, and poor software raids as such. The point with software
raid is that work that is otherwise done on the raid controller
hardware is done by the CPU and limited by the bus where the disks
live. The CPU in a modern PC is powerful, more powerful than
what most people use other than for brief, rare moments and so
can easily handle what it needs to handle. Hardware raid
controllers often simply don't have enough oomph in them to keep
up. My experience is that unless you've got a weak PC or want
to spend money on an expensive raid controller, software raid
is both more versatile, flexible, AND faster. And the MD driver
on linux is getting very, very good now.

> > 3. If I do a hardware RAID now, will I be able to move it to a computer
> > without RAID support but running Linux RAID
>
> I do not know the answer to that one.

The overhead issue, again. I can't imagine that working for
any raid controller, though I'd love to hear of counter-examples.

Bjørn
--
Bjørn Tore Sund "When in fear, and when in doubt;
(E-Mail Removed) Run in circles, scream and shout!"
Interaction! - Anonymous
http://www.interaction.worldcon.org.uk/

Evening,

On 2005-06-17, (E-Mail Removed) <(E-Mail Removed)> wrote:
> I just got a new Motherboard with inbuilt RAID0 capabilities over a
> pair of serial ATA hard disks.
>
RAID0 should only be used as a video editors scratch pad and nother else. I
seriously doubt you need to be able to shift data at 100MB/s, I would be
surprised if today's onboard 'RAID' controllers[1] could handle it yet alone
the bus on your machine. If you are trying to make Doom 3 run faster then
you should be looking at RAID1 as its access time you should care about and
not throughput.

If its for a fileserver, you really should check that the
OS/Motherboard/Switches are capable of saturating a 1Gbit network *link*.

I do not mean to sound cynical but I would guess RAID is more, for you at the
moment, a 'tickbox' you are wondering about turning on?

> 1. I was wondering if I will be able to take this pair of hard disks to
> another motherboard in the future and still be able to see all the data
> it has intact ( somebody told me that the motherboard supported RAID is
> specific to motherboard and that I will lose all the data if I change
> the motherboard )
>
If the motherboard is different you should expect that the data is
non-transferable. The moment you hit hardware RAID (the only disadvantage I
can think of) you are locked into that manufacturer and probably range of
RAID cards. With software RAID there usually is the migration to alternative
kit option.

> 2. How does the hardware raid compare with Linux raid support in terms
> of speed ?
>
As already said, far better than software RAID. You need to realise this is
*only* for throughput, you probably will actually notice the critical access
time is worse (higher) when compared to a single drive, it definately will be
no higher as for RAID0 to read/write to the drive both drives need to operate
in sync. As I said about , RAID0 is only useful in video editing, and then
only as a temporary scratch pad.

> 3. If I do a hardware RAID now, will I be able to move it to a computer
> without RAID support but running Linux RAID
>
Same as question 1, the answer too. This is very _unlikely_ to work. Expect
your data agin to be non-transferable.

Unless it says Adaptec on the tin son, don't touch it

Cheers

Alex

[1] el-cheapo and should not be trusted at all

> Thanks
> --sony
>

<(E-Mail Removed)> wrote in message
news:(E-Mail Removed) oups.com...

>I just got a new Motherboard with inbuilt RAID0 capabilities over a
> pair of serial ATA hard disks.

RAID0 means that if either drive fails, you're screwed. I would not
recommend it for anything except very special applications.

> 1. I was wondering if I will be able to take this pair of hard disks to
> another motherboard in the future and still be able to see all the data
> it has intact ( somebody told me that the motherboard supported RAID is
> specific to motherboard and that I will lose all the data if I change
> the motherboard )

Almost definitely not.

> 2. How does the hardware raid compare with Linux raid support in terms
> of speed ?

Unless you have really good hardware RAID or a really low-end CPU,
software RAID will be as good or better.

> 3. If I do a hardware RAID now, will I be able to move it to a computer
> without RAID support but running Linux RAID

Not likely.

DS