RAID 1 Question


B

Bruce.

I hope this is an easy RAID 1 question.

I have an ASUS P5E motherboard and the BIOS supports RAID arrays. I'm
using Windows 7 64 bits.

My question is if I run 2 drives in a RAID 1 mirror setup, what will
happen if the motherboard fries for any reason? Will I still be able to
get files off one of the disks in a different, perhaps non-ASUS motherboard?

In other words, are the drives each individually formatted as a standard
Windows volume so I could pluck out 1 of the drives and put it in a new
system without having to use RAID in the new system?

Thanks!
Bruce.
 
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P

Paul

Bruce. said:
I hope this is an easy RAID 1 question.

I have an ASUS P5E motherboard and the BIOS supports RAID arrays. I'm
using Windows 7 64 bits.

My question is if I run 2 drives in a RAID 1 mirror setup, what will
happen if the motherboard fries for any reason? Will I still be able to
get files off one of the disks in a different, perhaps non-ASUS
motherboard?

In other words, are the drives each individually formatted as a standard
Windows volume so I could pluck out 1 of the drives and put it in a new
system without having to use RAID in the new system?

Thanks!
Bruce.
If you're thinking of "getting files" off this thing, you're
looking at it the wrong way.

A RAID array doesn't absolve you from doing backups.

In addition to your two drive RAID 1 mirror, you've also
got a third drive with a backup on it. Why ?

It's to cover a power supply failure. If the power supply
puts out +15V on the +12V rail, both of the RAID 1 drives
are burned instantly. That's a single point of failure,
with no data to recover.

And that means, there needs to be a third drive, unpowered,
which is only connected when you're doing a backup. Or more
ideally, something like an external 3.5" USB enclosure with its
own power supply.

And that third drive, solves the "dead power supply" and
"dead motherboard" issue, at the same time. If you can't get
the data off whatever RAID format was used, there is always
your backup to rely on.

Now that you see the need for that, you have to ask,
"well, why am I using RAID 1 ?".

You use RAID 1, to defer maintenance. Say one of the
drives fails at 2PM in the afternoon. You don't want to
fix it right away. You continue working until 5PM, and then
you consider fixing it, after your work day is over. RAID
arrays help move the maintenance slot to a more convenient
time.

They're not an "automatic backup system", simply because
there are failure modes that can ruin all your data in one
shot.

To give another example, we had a couple RAID 5 arrays at
work. Due to a firmware bug (in a $$$ controller), it decided
to erase a block down near the origin of all the drives. The data
was rendered inaccessible instantly. The office staff ended up having
a picnic on the grass, outside the office building. The disks
had to be restored from tape, a three hour operation in the
middle of a work day, costing hundreds of thousands in lost
productivity. So what good is a RAID, when something other
than a disk failure occurs ? It's the failure modes you don't
know about, that kill you.

Or, how about the person, with a SIL3112 running RAID 1,
where one of the drives died. And then the owner discovers,
the other disk is *not* a mirror copy. The other drive
hasn't been updated by this scheme, for three months. And
the owner swears there were no warning dialogs, that the
SIL3112 was no longer mirroring. Just one remaining drive,
and three month old data.

In fact, your data would be recoverable. Typically, metadata
is stored on the drive, in a reserved area. If you move the
drive to a non-raid1 interface somewhere, the reserved area
is no longer reserved (which doesn't really matter, as you're
not about to modify the partition structure anyway). The information
about the RAID 1, stored in the MBR, would still be valid.

Even if the data is not immediately recoverable, it is all still there,
and copying it sector by sector, would undoubtedly give all
the data back. But I don't think it would be so tough. It's
other RAID formats, that potentially can take more work. Some
of the other RAID formats involve interleaving, and then
you'd have to "spend $39.95", to get a tool worthy of
recovering the data (i.e. move data from N small drives,
to one big drive). So if you had a RAID 5, and move all the
drives to another computer, then you'd need to de-interleave
the RAID info, to make a single drive containing the same info.

You can have a RAID 1 if you want. It might easily save
your bacon some day. But it can't solve every problem, which
is why you're still making backups. And that backup you make,
is your insurance, not the second drive in the mirror.

Paul
 
A

Anssi Saari

Bruce. said:
I hope this is an easy RAID 1 question.

I have an ASUS P5E motherboard and the BIOS supports RAID arrays. I'm
using Windows 7 64 bits.

My question is if I run 2 drives in a RAID 1 mirror setup, what will
happen if the motherboard fries for any reason?
Not for any reason, if the same reason fries the drives too.

Other than that, this would be Intel's software raid on that
motherboard I believe. So it's likely you can recover with another
board with Intel's software RAID.
In other words, are the drives each individually formatted as a
standard Windows volume so I could pluck out 1 of the drives and put
it in a new system without having to use RAID in the new system?
I've found it's really hard to find out even the simplest things about
a particular Raid system unless you try it for yourself and see. "Does
a drive in a particular Raid-1 array work alone?" Or "Does a
particular Raid-1 array stripe reads?"

I suppose the best way to decide this is to ask yourself "does
provided documentation cover the recovery case I'm worried about?" If
not, assume the worst and make sure you have backups.
 
B

Bruce.

You can have a RAID 1 if you want. It might easily save
your bacon some day. But it can't solve every problem, which
is why you're still making backups. And that backup you make,
is your insurance, not the second drive in the mirror.

Paul
Thank you for your backup advice.

My RAID 1 will not *replace* the extensive backups I already do. I've
had lighting strike multiple times that has taken out several components
at once, so I am a firm believer in several forms of backup and
redundancy. RAID 1 would simply add to my backups, and would supplement
the periodic backups I do in a more real time manner, reducing the
chance of loosing recent changes made in-between scheduled backups.

Hopefully someone else can more directly answer my question about how
RAID 1 volumes are formatted.

Bruce.
 
B

Bruce.

I've found it's really hard to find out even the simplest things about
a particular Raid system unless you try it for yourself and see. "Does
a drive in a particular Raid-1 array work alone?" Or "Does a
particular Raid-1 array stripe reads?"
It would save me a huge amount of time, expense, and trouble if someone
else already knows the answer.

Thanks.
Bruce.
 
D

DevilsPGD

In message <[email protected]> someone claiming to be
Bruce. said:
It would save me a huge amount of time, expense, and trouble if someone
else already knows the answer.
The answer is "try it and see", every RAID implementation is potentially
different and we don't know what exactly you have, or how it's
configured.

If your motherboard's implementation is a dumb port multiplier then it
will work. If it's an Intel RAID chip (which is mostly software RAID)
then it will *likely* work, as long as the new motherboard uses the same
chipset.

If your motherboard has an actual RAID controller of some sort (other
than Intel's) then it's a complete crapshoot.

There's no way to know for sure from your computer, if you want to be
certain, you need to pull a drive out and move it to another computer
and see what happens. You could use another SATA controller (and add-on
card, or a USB SATA adapter) rather than another computer, if that's
easier.
 
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R

Rob

I hope this is an easy RAID 1 question.

I have an ASUS P5E motherboard and the BIOS supports RAID arrays. I'm using Windows 7 64 bits.

My question is if I run 2 drives in a RAID 1 mirror setup, what will happen if the motherboard fries for any reason? Will I still be able to get files off one of the disks in a different, perhaps non-ASUS motherboard?

In other words, are the drives each individually formatted as a standard Windows volume so I could pluck out 1 of the drives and put it in a new system without having to use RAID in the new system?

Thanks!
Bruce.
The P5E uses the Intel ICH9R chipset, so it is extremely likely
that a (different model) replacement motherboard which has ICH9R
would be able to read them.
As others have mentioned, nothing is guaranteed when it comes to
RAID arrays though.
You should at least make a note of all of the current settings,
such as stripe size etc., and version of Intel Matrix RAID or RST
you have installed. As you mention that this is not your main
backup method in a leter posting, you should be covered in a
worst-case scenario; I have seen a blown PSU take-out every
drive connected to it in a system, including optical drives,
so crucial data backups really need to be kept on a physically
unconnected system.
The reason that you are not getting a simple answer is that
the RAID array configuration information can be held on a special
area of the drives (RIS for HP systems, for example) although it
may be held elsewhere on other implementations. As far as I know,
the format of that information can vary between implementations
and is probably proprietry and not released publically due to its
commercially sensitive nature.
I use imaging software (Acronis True Image Home) which can
image whole drives. Such an image held on an external or
network drive can be updated (rather than having to image the
whole drive each time) and temporarily mounted if I want to
to quickly recover individual files.
HTH
 
B

Bruce.

The P5E uses the Intel ICH9R chipset, so it is extremely likely
that a (different model) replacement motherboard which has ICH9R
would be able to read them.
As others have mentioned, nothing is guaranteed when it comes to
RAID arrays though.
You should at least make a note of all of the current settings,
such as stripe size etc., and version of Intel Matrix RAID or RST
you have installed. As you mention that this is not your main
backup method in a leter posting, you should be covered in a
worst-case scenario; I have seen a blown PSU take-out every
drive connected to it in a system, including optical drives,
so crucial data backups really need to be kept on a physically
unconnected system.
The reason that you are not getting a simple answer is that
the RAID array configuration information can be held on a special
area of the drives (RIS for HP systems, for example) although it
may be held elsewhere on other implementations. As far as I know,
the format of that information can vary between implementations
and is probably proprietry and not released publically due to its
commercially sensitive nature.
I use imaging software (Acronis True Image Home) which can
image whole drives. Such an image held on an external or
network drive can be updated (rather than having to image the
whole drive each time) and temporarily mounted if I want to
to quickly recover individual files.
HTH
Ok, thanks. I guess it wasn't as simple as a question as I had hoped.
I also use True Image too as my primary backup method across the network
to other hard drives.

I was hoping that RAID1 would supplement my True Image backup system,
but I'm not going to attempt it if I can't be sure each of the RAID1
volumes is bootable/readable in another non-RAID PC. If lightning fried
my motherboard and 1 of the drives, the other drive would then be
useless to me.

Bruce.
 
P

Paul

Bruce. said:
I was hoping that RAID1 would supplement my True Image backup system,
but I'm not going to attempt it if I can't be sure each of the RAID1
volumes is bootable/readable in another non-RAID PC. If lightning fried
my motherboard and 1 of the drives, the other drive would then be
useless to me.

Bruce.
As far as I know, your C: partition would be stored contiguously on
the drive, so in that sense, the information is not lost. It starts
at some sector, ends at some other sector.

I can give you a strange example, of what happens when metadata is
used in some of these schemes. I had a Promise chip interface and
an Intel chip interface. No RAID was involved, both devices being used
in what was claimed to be a single disk mode (the Promise would be JBOD).

Three partitions were prepared, while the disk was connected to the Intel
chip.

When the disk was moved to the Promise interface, the first partition would
disappear (not be mounted, and no complaints). Moving the disk back to
Intel, all three partitions would be present.

The partition was not damaged, it just wouldn't mount. Which means either
something was offset, or masked, and that prevented it from mounting.

As long as some interface could be found, that could give access to the
data containing sectors, the partition could be copied to some other,
uncompromised storage. The "dd" command, for example, will copy an
arbitrary set of contiguous sectors, and a port of that is available
for Windows.

So the thing is, a partition may refuse to mount, when moved to another
interface, but unless you make a concerted effort to write over top
the (misconfigured) setup, your data is still there. And there are
tools that can find it for you (Testdisk being just one of them).

If it was easy, how would computer repair people stay in business ? :)

Paul
 
R

Rob

Ok, thanks. I guess it wasn't as simple as a question as I had hoped. I also use True Image too as my primary backup method across the network to other hard drives.

I was hoping that RAID1 would supplement my True Image backup system, but I'm not going to attempt it if I can't be sure each of the RAID1 volumes is bootable/readable in another non-RAID PC. If lightning fried my motherboard and 1 of the drives, the other drive would then be useless to me.

Bruce.
Well, it does still supplement it, but not completely.
RAID1 is still very useful as there is definitely a non-zero
chance that one of the hard drives will just go bad randomly.
Simply popping-in a new drive and then continuing with your work
while the mirror is rebuilt in the background may be a huge plus,
if you are in business for example.
It all depends where you want to draw the line - some firms
buy 2 of everything, so have an identical spare motherboard
available for the lightning strike scenario you describe.
The PC I'm using now has a RAID1 boot drive for uninterrupted
working reasons, but actual data is stored on a network with
robust real-time backup. Glad I didn't have to pay for that
aspect though! :blush:)
Cheers
 
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B

Bruce.

Well, it does still supplement it, but not completely.
RAID1 is still very useful as there is definitely a non-zero
chance that one of the hard drives will just go bad randomly.
Simply popping-in a new drive and then continuing with your work
while the mirror is rebuilt in the background may be a huge plus,
if you are in business for example.
But it also comes with a price if the RAID1 drives are non-standard
formats. Right now if I lose the motherboard, I have a perfectly
readable drive to move to a new PC.

On the other hand, if I lose the motherboard in a non-standard RAID1
setup, I end up with 2 perfectly good but completely unreadable drives.

So unless the RAID1 drives are readable in a non-RAID PC, that seems
like a huge step backward in the chances of a successful disaster recovery.

I checked Newegg and my current motherboard is no longer in stock.

Bruce.
 
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