RAID1 - what happens if your motherboard RAID controller dies?

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clangers_snout

I have a motherboard with a hardware RAID controller built in and I
intend to set up two identical drives in RAID 1 configuration. My
worry is how I would go about recovering the data from either drive if
my motherboard goes down. I assume that you can't just plug one of the
drives in to another motherboard and expect it to be read by a normal
SATA2 (in my case) connection. So how would I recover the data in this
worst case condition?
 
In said:
I have a motherboard with a hardware RAID controller built in and I
intend to set up two identical drives in RAID 1 configuration. My
worry is how I would go about recovering the data from either drive if
my motherboard goes down. I assume that you can't just plug one of the
drives in to another motherboard and expect it to be read by a normal
SATA2 (in my case) connection. So how would I recover the data in this
worst case condition?

Coingratulations, you have found one inherent porblem with
hardware-RAID (as opposed to software RAID).

Having a spare mainboard is handy. This has all sorts of
problems, e.g. whai if the CPU dies and a replacement
is difficult to obtain. Controller card is a little better
but not oo much. There is RAID recovery software,
but it costs money.

I would advise to use software RAID instead, as here
you can just move the drives to a different machine.

Arno
 
I have a motherboard with a hardware RAID controller built in and I
intend to set up two identical drives in RAID 1 configuration. My
worry is how I would go about recovering the data from either drive if
my motherboard goes down. I assume that you can't just plug one of the
drives in to another motherboard and expect it to be read by a normal
SATA2 (in my case) connection. So how would I recover the data in this
worst case condition?

You would need to replace the motherboard anyways, and that would fix
the problem (assuming the motherboard hasn't been discontinued).
 
I have a motherboard with a hardware RAID controller built in and I
intend to set up two identical drives in RAID 1 configuration. My
worry is how I would go about recovering the data from either drive if
my motherboard goes down. I assume that you can't just plug one of the
drives in to another motherboard and expect it to be read by a normal
SATA2 (in my case) connection. So how would I recover the data in this
worst case condition?

It depends entirely on the mobo/controller(s) in question. For example, I
have a customer whose MSI socket 754 mobo failed, this had 2 SATA srives in
Raid1. I got him a new board, an Intel P35 based one, so different kit all
round. I attached one of the drives in normal mode and it was read
immediately, just needed to change the drivers and we were up and running. I
then just added the 2ns drive back and rebuilt the Raid.
This does not mean however that it will work this way every time, you just
have to suck it and see sometimes.
 
I have a motherboard with a hardware RAID controller built in and I
intend to set up two identical drives in RAID 1 configuration. My
worry is how I would go about recovering the data from either drive if
my motherboard goes down.

You do? What is your assumption based on?
that you can't just plug one of the drives in to another motherboard
and expect it to be read by a normal SATA2 (in my case) connection.

No? Why not? Have you tried?
So how would I recover the data in this worst case condition?

Not, based on your assumption.

How does the word "backup" sound to you?
 
It depends entirely on the mobo/controller(s) in question. For example, I
have a customer whose MSI socket 754 mobo failed, this had 2 SATA srives in
Raid1. I got him a new board, an Intel P35 based one, so different kit all
round. I attached one of the drives in normal mode and it was read
immediately, just needed to change the drivers and we were up and running. I
then just added the 2ns drive back and rebuilt the Raid.
This does not mean however that it will work this way every time, you just
have to suck it and see sometimes.

The issue here is where the RAID stores its metadata. If in EEPROM,
you are fine. If on the end of the disk, you are fine as well.
If at the beginning of the disk, it gets difficult.

But, true, for RAID1 you may get lucky. I would advise you to
try removing a disk and reading it non-raided in a different
computer. If that works, it should also work in the future ;-)

Arno
 
I have a motherboard with a hardware RAID controller built in and I
intend to set up two identical drives in RAID 1 configuration. My
worry is how I would go about recovering the data from either drive if
my motherboard goes down. I assume that you can't just plug one of the
drives in to another motherboard and expect it to be read by a normal
SATA2 (in my case) connection. So how would I recover the data in this
worst case condition?

You assume incorrectly, in every RAID1 setup I've seen. Each member can be
accessed as a stand-alone drive if necessary, on a normal controller.

Whatever on-disc configuration information there is resides outside the normal
disc layout (partition, LVM, whatever).
 
Arno Wagner wrote in news:[email protected]
The issue here is where the RAID stores its metadata. If in EEPROM,
you are fine. If on the end of the disk, you are fine as well.
If at the beginning of the disk, it gets difficult.

Difficult, babblebot?
But, true, for RAID1 you may get lucky.
*I would advise you*

Don't you love the sound of that.
He get's corrected yet immediately starts to advise again.

Maybe this time his advice is better, no?
to try removing a disk and reading it non-raided in a different computer.
If that works, it should also work in the future ;-)

Or not.
Babblebot's way of saying he didn't understand at all what previous poster was saying
 
SteveH wrote in news:[email protected]
Squeeze wrote:

Some context restored:
I was gonna say, that's what I said,

Why would the babblebot repeat what you said?
more or less.

It's obviously gonna work in that particular computer that he would
have checked it in but that doesn't mean it will work in any new
computer he might buy when/if the actual incident is going to happen.
By the time it happens computers without RAID capability may not be
available anymore. RAID controllers may well check in specific places
for any evidence of previous raid implementation and refuse to accept
it when its not their own, even if you want to use it as non-raided.
To avoid such unwanted behaviour the RAID capability must be able
to be switched off entirely.

Like you said, it depends. That's not what the babblebot said.

If want to be sure, have backups.
 
I should elaborate on what I wrote above. A RAID1 does need
the metadata to exist and be understood by the controller
(which must have the RAID1 funcitonality) in order to
continue functioning as a two drive mirror of a single
logical volume but that is not necessary to read the data
off either member alone.

True. There are RAID 1 controllers, however, that put the
metadata at the beginning od the disk and translate everything
after. I don't know how common that is today, but it used to be
a problem. If you can take a disk out of a RAID1 and access
it without any special measures (LVM translation, e.g.) on
a non-RAID controller, then the metadata is very likely at
the end or not on disk at all.

Reasons for putting the metadata at the beginning are the
usual: Lazyness, stupidity or a desire to bind you to
a specific product.

Arno
 
Good discussion, learned a lot of it, since I've got the same thoughts
like starter clangers_....
Question: To me it seems like ICH9R from Intel is popular at the
moment for constructing RAIDs. Might be true or not. But, given the
ICH9R, where does it put these metadata? Does anybody know? Any
experiences anybody about pulling off one RAID1-drive from an ICH9R to
whatever SATA-connector? Does this single special thing out of the big
variety of RAID-Levels and controllers work?

Reagrds,
Frank
 
Frank said:
Good discussion, learned a lot of it, since I've got the same thoughts
like starter clangers_....
Question: To me it seems like ICH9R from Intel is popular at the
moment for constructing RAIDs. Might be true or not. But, given the
ICH9R, where does it put these metadata? Does anybody know? Any
experiences anybody about pulling off one RAID1-drive from an ICH9R to
whatever SATA-connector? Does this single special thing out of the big
variety of RAID-Levels and controllers work?

Reagrds,
Frank

I think the answer to this one is simple.

You don't need to know where the metadata is stored :-)

Why ? Because RAID1 is not a substitute for backups.

Consider the following scenarios.

1) You download a virus. It zeros a single sector in the middle
of every MP3 file you have stored on the computer. Does the
RAID1 mirror protect from this fault ? No. Both disks have
the exact same (virus damaged) files stored on them.

2) Consider the power supply fails in the computer. The 12V rail
rises to 15V. The motors on both hard drives are burned instantly.
Does the RAID1 help you now ? No. Both disks are dead. Same
thing, if there was an electrical storm passing overhead, and
your house AC is hit. Both motherboard and drives could be
ruined.

That is why you have daily backups - incremental and full backups.
If the computer is destroyed, you reach for that USB external enclosure
you use on a daily basis, and you do a cold metal restore to
the newly constructed computer. Now it doesn't matter where the
metadata is. Because the backup image has captured the data.
By storing the USB external enclosure in a safe place, away
from the computer, there are better odds it'll survive an
act of God.

Another point. If you're going RAID1, connecting the computer
to an uninterruptible power supply. If the uninterruptible power
supply has a serial cable to connect to the back of the computer,
that will allow an automated and orderly shutdown if you aren't
present when the power goes off. That will help maintain the exact
mirroring of your RAID1 drives. Otherwise, an abrupt shutdown, could
leave divergent contents.

Paul
 
I think the answer to this one is simple.

You don't need to know where the metadata is stored :-)

Why ? Because RAID1 is not a substitute for backups.

Excuse me, Paul, but there is one thing I don't like: "You don't need
to know", since "I like to know!"

Let me explain: Raid 1 is no substitute for a backup, that's correct.
But if I receive RAID for free (with a P35 mainboard) and considering
the cost for a second hard drive (70 Euros for 0.5GB), it's simply
worth the money.

What I mean is: I pay 70 Euros for the second drive and I receive the
assurance "if a disk crashes (and only in that case) you'll have a
second one with the identical content". Nothing else! No virus
protection, no power problem protection, no whatsoever protection,
only "if one drive fails, the other has the copy and you don't need to
spend money, time and nerves to reconstruct from backup." Of course,
if the system blows up for any other reason, it's very helpful to have
a backup.

On the other hand, my personal statistic:I'm in that business for
nearly twenty years, I've started with a 20 MB MFM-harddrive (yes,
kids, it weight a few kilos!). In that time, I've experienced no virus
problem, no power problems, nothing, but two hard drives crashed in
only 27 months (1st an IBM and 2nd a Samsung). This is my personell,
not representative experience.

And after all these words: Does anybody know, what ICH9R does
(following the discussion of this thread)?

Kind regards
 
Frank said:
Excuse me, Paul, but there is one thing I don't like: "You don't need
to know", since "I like to know!"

Let me explain: Raid 1 is no substitute for a backup, that's correct.
But if I receive RAID for free (with a P35 mainboard) and considering
the cost for a second hard drive (70 Euros for 0.5GB), it's simply
worth the money.

What I mean is: I pay 70 Euros for the second drive and I receive the
assurance "if a disk crashes (and only in that case) you'll have a
second one with the identical content". Nothing else! No virus
protection, no power problem protection, no whatsoever protection,
only "if one drive fails, the other has the copy and you don't need to
spend money, time and nerves to reconstruct from backup." Of course,
if the system blows up for any other reason, it's very helpful to have
a backup.

On the other hand, my personal statistic:I'm in that business for
nearly twenty years, I've started with a 20 MB MFM-harddrive (yes,
kids, it weight a few kilos!). In that time, I've experienced no virus
problem, no power problems, nothing, but two hard drives crashed in
only 27 months (1st an IBM and 2nd a Samsung). This is my personell,
not representative experience.

And after all these words: Does anybody know, what ICH9R does
(following the discussion of this thread)?

Kind regards

The metadata position is not public knowledge. If you want to know,
you connect a disk to an Intel Southbridge, create a RAID volume, and
then search for the sector or sectors that have changed.

There is a reasonable chance, that if you took a hard drive connected
as RAID1, on a ICH6R, it would work on a ICH9R. There should be continuity
in the forward direction. There might not be in the reverse direction
(as ICH9R might support RAID5, and ICH6R doesn't, and ICH6R RAID BIOS
won't know what RAID5 is).

The only other company, that offers some kind of statement about
compatibility between controllers, was Promise. Whether that is still
true, is unknown to me.

The reason no public statements are made, is it allows the companies
involved, to change the metadata format, any time they choose, without
warning to the public. As technical requirements merit.

As an example of my own, personal experience. I connected a drive
to a Promise controller (perhaps PDC20378), and discovered that the
first partition was no longer visible. So at least in the case
of that chip, and the metadata it was using, there was some problem
seeing a partition, when moving between an Intel chip and a separate
Promise PDC20378. Tomshardware did an article, some time ago,
where they tried something similar. I had my own theories as to
which test cases would work, and which ones would not. Virtually
any heterogenous case, failed. Some of the homogenous cases
(moving Promise array to another Promise card), worked.

But I don't see any categorical statements being possible, unless
these companies take inter working as a serious technical requirement.

You can buy two PCI or PCI Express controller cards, and put one away
for the day when the first one fails. As some of the cards are dirt
cheap (such as some of the old SIL3112 dual port cards), that is not
such an expensive alternative. But the performance and reliability
of these solutions, leaves a lot to be desired. For example, at
least one person has seen a SIL3112 operating in RAID1 mode,
where the RAID stopped "mirroring" for a period of three months.
When one of the disks died, the data available on the other disk
was "stale" and as near as the poster could determine, about
three months old. Based on that kind of performance, I'd want a
solution that is a bit better behaved.

I'd feel much better about motherboard RAID1 solutions, if I
knew the controller firmware or software, was auditing how
identical the disks were, during idle moments. I'm not aware
of any of these solutions, auditing their own performance.

Based on a few factors like that, I feel a backup is still
a wise investment.

Paul
 
In comp.sys.ibm.pc.hardware.storage Frank said:
Good discussion, learned a lot of it, since I've got the same thoughts
like starter clangers_....
Question: To me it seems like ICH9R from Intel is popular at the
moment for constructing RAIDs. Might be true or not. But, given the
ICH9R, where does it put these metadata? Does anybody know? Any
experiences anybody about pulling off one RAID1-drive from an ICH9R to
whatever SATA-connector? Does this single special thing out of the big
variety of RAID-Levels and controllers work?
Reagrds,
Frank

I don't know what exactly Intel does, but it seems Linux dmraid
(the fakeraid driver) can access intel RAID arrays. That means
even without the controller the disks are accessible with Linux.

It seems Intel stores the metadata in the last two sectors of the
disk (but I found no hard evidence, just heresay). If true,
that would mean that you can use the individual disks in a RAID1 on
any non-raid controller.

Arno
 
In comp.sys.ibm.pc.hardware.storage kony said:
On Mon, 26 May 2008 11:01:04 -0700 (PDT), Frank
Some who have mentioned metadata at the start of a drive are
muddying the waters, like saying it's possible there are
pink elephants even though they are rare. Odd things
happened years ago but today there's one thing to say about
metadata on the start of a drive - don't use a controller
that does this if you can ever find one.
Practically every modern raid controller puts the metadata
on the rear end of the drive.

Good to know that this design mistake is now typically
fixed. People may still have older hardware or get older
hardware from eBay, for example. In that case they need
to be aware of the potential problem.
You can test this easily
enough, if you can take a drive with data on it, define it
as a source or primary in the raid configurator for a raid1.
and still retain all data.

Huh? This does not seem to make any sense.

Here is what you can do (linux):
1) Attach dribe to a non-RAID interface or configure it
as pass-trough/raw. Blank the start of a drive with zeros
head -c 10240 /dev/zero <drive>
Overwrites the firsth 20 secotrs with zeros. Should
be enough
2) Create a RAID on this disk with your controller.
3) Re-attach it in the form in 1) and look at the
first 20 sectors, e.g. by doing
head -c 10240 <drive> | hex

I anything was changed, be wary. This controller may put
the metadata at the satrt or mess with the MBR. Both not
good.

Arno
 
kony wrote in news:[email protected]
Well, "that doesn't mean it will" is true, but irrelevant -

If the drive is rejected then that's very relevant.
the variable is not whether that worked, only whether the original
system uses a standard config which can take a drive with data
already on it and add that as a source member of a RAID1 array.
*If* it can do that, [then] there is no reason to believe it will make any
changes to the drive

Why not. There must still be information stored /somewhere/ that sig-
nals whether the drives are in sync or that the mirror needs to be rebuilt.
Such information won't be on a standard non-raided drive.
that would prevent use in any other system

Well, that's up to the people who designed/wrote the particular RAID
bios of that other system. I can't speak for them and neither can you.

[snip]
 
Arno Wagner wrote in news:[email protected]
True. There are RAID 1 controllers, however, that put the metadata
at the beginning od the disk and translate everything after. I don't
know how common that is today, but it used to be a problem. If you
can take a disk out of a RAID1 and access it without any special
measures (LVM translation, e.g.) on a non-RAID controller,
then the metadata is very likely at the end

Or at the 'beginning'.
"Beginning" is a relatively imprecise description, Babblebot.
Where does it say that "beginning" has to be sector 0, eh?
or not on disk at all.

There should at least be some extra information to control the validity
and status of the configuration.
Reasons for putting the metadata at the beginning are the usual:
Lazyness, stupidity or a desire to bind you to a specific product.

Or just because there is enough unused space near the start of the drive
that can be used for it's own purposes without interfering with standard
partitioning and/or formatting, Babblebot.
 
I'd feel much better about motherboard RAID1 solutions, if I
knew the controller firmware or software, was auditing how
identical the disks were, during idle moments. I'm not aware
of any of these solutions, auditing their own performance.

I prefer RAID 5 for this very reason - it's most unlikey to unRAID itself
without you knowing anything about it. Also, there is less faffing around if a
disk does dir - just plug in the replacement and rebuild. Of course that
doesn't get round the different controller problem but there you go.
 
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