Creating RAID 1 Array: Will it wipe out existing data?

  • Thread starter Thread starter Randy
  • Start date Start date
R

Randy

I know that you can add a drive after the array is created. But during
creation of a RAID 1 array, will the data on both drives be erased? In
other words: can you use an existing HD to create a RAID array then add the
other drive and have it copy the data to it?
 
Randy said:
I know that you can add a drive after the array is created. But during
creation of a RAID 1 array, will the data on both drives be erased? In
other words: can you use an existing HD to create a RAID array then add the
other drive and have it copy the data to it?
Click to expand...


In theory you can do this, i.e. use an existing drive with data and have the
data copied onto the 2nd drive as a mirror. At least that is what the
manual and the help file coming with the P4P800 indicates, regarding the Via
controller within.

I tried to do exactly this while setting up the array on my new board
several days ago. Windows 2000 apparently never had a chance to read this
manual and somehow in the setup process the partitions on both drives were
deleted. In fact, it took me more than a few minutes to realize why the
drives in my newly created array didn't show up in Windows Explorer. The
reason was that they had no partitions any longer and hence were not
formatted.

What I'm saying is I think there is a way to do this however the process is
counterintuitive, or at least it was to me.

Fortunately, I had the data all backed up, plus I ghosted it before I
attempted this.

I suggest that you try to do this, e.g. set up the array with existing data
on a drive. But, don't depend on it. Have all your data backed up, so that
if the system eliminates your partitions and your data by extension -- that
it is just a minor inconvenience. Then, you can just format the drives
(they will show up as just 1 drive because they are a mirror set) and put
your data back on them.

Good luck.

ken
p.s. my suspicion is that you will end up with a cleaner install and a
"better" mirror if you just forget about this, let the partitions be
deleted, then put your data back on the drives. In that case, you will get
a perfect copy on both drives.
 
Ken Fox said:
In theory you can do this, i.e. use an existing drive with data and have the
data copied onto the 2nd drive as a mirror. At least that is what the
manual and the help file coming with the P4P800 indicates, regarding the Via
controller within.

I tried to do exactly this while setting up the array on my new board
several days ago. Windows 2000 apparently never had a chance to read this
manual and somehow in the setup process the partitions on both drives were
deleted. In fact, it took me more than a few minutes to realize why the
drives in my newly created array didn't show up in Windows Explorer. The
reason was that they had no partitions any longer and hence were not
formatted.

What I'm saying is I think there is a way to do this however the process is
counterintuitive, or at least it was to me.

Fortunately, I had the data all backed up, plus I ghosted it before I
attempted this.

I suggest that you try to do this, e.g. set up the array with existing data
on a drive. But, don't depend on it. Have all your data backed up, so that
if the system eliminates your partitions and your data by extension -- that
it is just a minor inconvenience. Then, you can just format the drives
(they will show up as just 1 drive because they are a mirror set) and put
your data back on them.

Good luck.

ken
p.s. my suspicion is that you will end up with a cleaner install and a
"better" mirror if you just forget about this, let the partitions be
deleted, then put your data back on the drives. In that case, you will get
a perfect copy on both drives.
Click to expand...

That is why I do not bother to have RAID in my PC. Just buy another IDE hard
disk,
copying all files and data needed to backup, and probably some ghosted CDs,
etc.
then I can rest without worry.
 
Maximus said:
That is why I do not bother to have RAID in my PC. Just buy another IDE hard
disk,
copying all files and data needed to backup, and probably some ghosted CDs,
etc.
then I can rest without worry.
Click to expand...

I think the whole idea of a RAID array only makes sense if you have a
minimum of 3 drives; the first being a system disk with the OS on it, and
the latter 2 being the RAID array with your data. The whole idea of a
private person at home having a RAID array in their home PC would have been
pretty ridiculous even a year ago, but now, with HD prices so cheap as to be
laughable, especially after some of those outrageous rebate deals, it is
do-able.

But my suspicion (untested) is that a RAID array for a 2 disk system,
especially a RAID type "1" setup, would be pretty slow. If all you have is
data on the RAID disks, however, I doubt you would notice any speed
decrement.

If you want to REALLY go overboard, do what I just did; set up a 4 disk
system with disks 3 + 4 being the RAID "1" array, disk 1 being the OS disk,
and disk 2 being a repository for regular ghost images. Norton Ghost (or
other disk imaging programs) work extremely fast across a system bus. I can
image my system disk in several minutes so it is pretty painless. If you
ghost your OS disk every week or so, you are protected from most any
calamity short of a housefire, and of course the RAID "1" protects your data
itself.

ken
 
Randy said:
I know that you can add a drive after the array is created. But during
creation of a RAID 1 array, will the data on both drives be erased? In
other words: can you use an existing HD to create a RAID array then add the
other drive and have it copy the data to it?
Click to expand...

Yes, that´s no problem with Promise RAID-Controllers Asus is using on
their motherboards. Should be possible with RAID-Controllers from Intel too.

Christian
 
Hi Ken,
Ken Fox said:
I think the whole idea of a RAID array only makes sense if you have a
minimum of 3 drives; the first being a system disk with the OS on it, and
the latter 2 being the RAID array with your data. The whole idea of a
private person at home having a RAID array in their home PC would have been
pretty ridiculous even a year ago, but now, with HD prices so cheap as to be
laughable, especially after some of those outrageous rebate deals, it is
do-able.
Click to expand...
Given the prices of 'fairly' small ata133 drives these days and that some
folks seem willing to spend £300 or so on a graphics card:-), it seems to
me that 4 x 80gig PATA or SATA drives in a raid 1+0 array would be
ideal if one had another ATA drive on a non raid controller to boot from
so there would be better data security and the ability to chose to boot
from either the raid setup or a non raid one:-)
But my suspicion (untested) is that a RAID array for a 2 disk system,
especially a RAID type "1" setup, would be pretty slow. If all you have is
data on the RAID disks, however, I doubt you would notice any speed
decrement.
Click to expand...

Do you think there would be any real slowdoen in a raid 1+0 array, as
one part would be striped and that would be mirrored?

I've run a small 20gig striped set, with another drive on the 2nd port
to boot from, but there was always the worry that one drive in the
stripe might go down thus loosing the lot apart from my boot drive..
Now I have ended up with 2 raid controllers, one ata100 and one
SATA150:-) But only PATA drives... I guess it may be time to
organise a small xmas pressie for my rig:-) 4 x SATA drives to
see what they perform like..

RD
 
RD said:
Hi Ken,
Do you think there would be any real slowdoen in a raid 1+0 array, as
one part would be striped and that would be mirrored?
Click to expand...

Hi,

I'm no expert on this stuff so hopefully someone who is can give guidance.
It took some bumbling around for me to even figure out how to get the RAID 1
set up, and if I hadn't recently purchased a whole bunch of drives with huge
multi-rebates, I'd never have done it in the first place.
I've run a small 20gig striped set, with another drive on the 2nd port
to boot from, but there was always the worry that one drive in the
stripe might go down thus loosing the lot apart from my boot drive..
Now I have ended up with 2 raid controllers, one ata100 and one
SATA150:-) But only PATA drives... I guess it may be time to
organise a small xmas pressie for my rig:-) 4 x SATA drives to
see what they perform like..

RD
Click to expand...

I think that the major benefits of SATA drives are yet to be implimented.
At current speeds of 150 they are only slightly faster than the ATA 133 IDEs
being sold now.

Good luck,

ken
 
I did a "dry run" with a pair of SATA drives using the RAID utility built
into the Via chipset. The first warning it gave me when starting to
"create" the RAID 1 array was "all existing data on BOTH drives will be
deleted."
 
Randy said:
I did a "dry run" with a pair of SATA drives using the RAID utility built
into the Via chipset. The first warning it gave me when starting to
"create" the RAID 1 array was "all existing data on BOTH drives will be
deleted."
Click to expand...

the screens that appear in the helpfile did not occur on my desktop no
matter what I tried.

good luck
 
The bus transfer rate is not the bottleneck anyway with current drives, they
don't generally come close to 150 MB/sec in sustained transfer rate.
However, there are some upcoming improvements that should improve
efficiency, like Native Command Queuing, which allows the drive to better
decide how to efficiently handle requests..
 
In general, yes, this should be possible. Whether you can actually do it,
and how, depends on the RAID controller. I've not done much with IDE RAID
setups, but on the SCSI setups I've used, there's been an option to tell the
setup program NOT to initialize the drives when you create the array. Then
you have to make it rebuild the contents of the new drive - either it will
ask you when you create the array which drive's data you want to keep, or
you have to invalidate the contents of the new drive in the eyes of the
controller somehow to force a rebuild.
 
Back
Top