RE: Adding a disk to a RAID array

You are wrong about something. From the point of view of RAID controller,
there is an extra drive that gets merged with the other 3, to form a big
one. From what you point out is that you have only one drive created by the
RAID controller. This one drive is partitioned in 6 partitions sda1-sda6.
The procedure I mentioned is equivalent in simpler terms to removing a small
HDD (sda) and placing in a bigger one. If you create in the controller two
logical drives (No longer is possible to use RAID5 anymore-need at least 3
drives), you may put the OS in the partitions of one drive. It changes
little in capacity needs. These partitions will show up as sda1-sdax. The
other drive that will be created to hold the data will be visible as sdb.

With your current setup the only option is to backup THE WHOLE SYSTEM,
delete sda drive, recreate it again, install the OS and restore the data.
During OS installation you can leave more space to /data partition.
I do not know if your RAID controller has any option of adding the disk in
the array without losing data. This is something that you must check.

Sincerely
Mr. Olsi Lulani


-----Original Message-----
From: Elizabeth R Martin [mailto:[email protected]] 
Sent: Friday, March 14, 2003 5:08 PM
To: [email protected]
Subject: Re: Adding a disk to a RAID array

Lulani,

You are correct in that the OS sees only 1 drive /dev/sda because the
hardware
raid controller card takes care of all the RAID stuff.  I am rung RAID 5
currently with 3 drives, I want to add a 4th, it has been sitting in a
cabinet
for when needed.  The drive is then partitioned according to the information
I
posted sda1, sda2, etc.  Once I get the new hard drive installed in the BIOS
of
the controller card, it will create the /dev/sda seen by the OS as a larger
drive with the end of the drive not being used.  I know that I have to some
how
edit fdisk manually so that sda4, the extended partition, ending # shows the
new
end of the partition.  I then have to manually edit fdisk again so that the
ending # on sda6 shows the end of the partition and then restore the data.
Like
I said I remember manually doing this once before a long time ago but the
Unix
Guru who helped me then is no longer here.  This is something that I will
have
to plan downtime for since this is a critical system and I don't want to
make to
many mistakes with the changes.

Hope this information clears up any questions.

Elizabeth Martin

LULANI Olsi wrote:

> >From what you are stating it seems that the RAID is implemented in HW. As
a
> result the OS does not see anything. All the RAID stuff shows up as single
> drive. The point that you have to back-up all the data in the data
partition
> is that the partition during the reconfiguration of the controller will be
> deleted and recreated. Say you have two drives and later it will have
three
> drives. The drive will seem the same to OS. The only difference will be
the
> space it contains. At this point you will restore all the data from backup
> and the partition will seem to be the same as before but with more free
> space.
>
> Sincerely
> Mr. Olsi Lulani
>
> -----Original Message-----
> From: Elizabeth R Martin [mailto:[email protected]]
> Sent: Friday, March 14, 2003 4:01 PM
> To: Red Hat 7.2
> Subject: Adding a disk to a RAID array
>
> I am not sure where to start so I will just jump right in.  Up until
> last week I had the manual for the SCSI card in my hand and now it has
> managed to disappear.  I am still looking for it, although I have found
> a generic one from Adaptec that I have printed out and will go through.
> Hopefully I will be able to find out what I need to know concerning the
> hardware recognition of a new drive in the array.
>
> Hardware info:
> DPT (bought out by Adaptec) PM2654 I20 BIOS SmartRAID V controller card,
> firmware updated last April
> 3   SCSI Hard drives  36gb Segate
>
> Here's the problem:
>
> I have a SCSI hardware RAID array of 3 drives.  Space is running out on
> the data partition of the array and I need to add another 36gb drive to
> the array. I think that all I need to do for the drive to be seen by the
> hardware is to install the drive and boot up however, I am still looking
> in to that.  Here is the partition information:
>                    start        end     mgb      part type     mounted
> /dev/sda
>    - sda1         1            9        71        ext3            boot
>    - sda2        10         270    2047      Linux-swap
>    - sda3       271        336     518       ext3            tmp
>    - sda4      337        8924   67366    Extended
>        - sda5  337         859    4103      ext3
>        - sda6  860        8924   6324      ext3            data
>
> I want to add the new drive space to the end of sda6 and into the
> mounted data partition but I have not been able to find out any
> information on how to do this.  I have looked through a stack of books,
> asked those in the "know" here at work and no one seems to be able to
> tell me how to do it.  I know that I will have to back every thing up in
> the data partition before doing this.  I also know that I have to do
> something in fdisk.  I once did something like this to a non RAIDed
> Alpha Ultrex system about 6yrs ago but have no idea of how to proceeded
> here.  I am trying not to have to reinstall the entire system just to
> install a new drive.
>
> Assistance is greatly appreciated.
>
> Elizabeth R. E. Martin
> Network Support Specialist
> UT-Houston Medical School
>
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