RAID 5 on a Dell Poweredge Server

Stky10

We've bought a Poweredge 2800 as a domain controller in
work. We got it with four 73Gb disks, which I planned on
setting up as two disks, as a mirror of each other (ie b mirrors
a, d mirrors c).

When we were purchasing it Dell said they'd configure it
with a RAID 5 controller and set it up with a default configuration
which we could easily change with the OpenManage software they
package with the server.

Anyway, now that we've received the server, it looks to me
more like that OpenManage merely tells me how the server
is configured rather than being able to change it as we were
told. They've set up the four disks in to a single array, and
it has a 12Gb C:\ partition, and the rest as a \ partition,

So I'm thinking that the only way of changing this would mean
wiping the system and starting from the start. Is this the
case??

Also, if I decide to keep it as it is, if there is a RAID 5 controller
being used, is the system writing to the disks in RAID 5 automatically,
or is it something I have to setup manually myself within Windows,
or how do I check for this??

Capt'n Midnight

the array manager software should tell you the name of the card
or look inside diskmanager in windows - if they aren't using a HW raid card then it has to be software raid and disk manager will show the disks.

Deep breath time + device=fngrcrss.sys
power down and move the 4th drive to a different slot
power up and hopefully it boots on the remaining 3 - if not moan to dell about raid 5 not being setup properly and how you could have lost data

use openmanage to setup 4th drive as single drive
now use disk admin to software mirror C:

now take out all drives and try to boot up server off the single drive - if ok can now break the sw mirror in disk admin and use open manage to hw mirror them..

A lot of work - best to leave as RAID 5 - unless you are using something like exchange where it's better to have the different drives for different processes.

Another option would be to software mirror the spare drive C: to a new RAID 5 array on the remaining three disks and the use the 4th as a hot spare.

JDxtra

Nope, the Openmanage bootable CD (server assistant I think it's called) should allow you to configure the disks what ever way you want.

The Openmanage application used from within Windows won't allow you to reconfigure the drives from RAID5 to two seperate mirrors (as Windows has already loaded from that array).

My advice: do it right from the start. Boot from the server assistant CD, click server setup, blow away the existing RAID config, setup your two mirrors and let the server assistant complete the OS install for you. Should take now more than 30 minutes for a basic server install.

power down and move the 4th drive to a different slot
power up and hopefully it boots on the remaining 3 - if not moan to dell about raid 5 not being setup properly and how you could have lost data

Doing this will cause errors on boot up, and the server will probably emit an alert tone.

I'm also not convinced about having software mirrors and hardware redundancy operating at the same time.

Capt'n Midnight

jdempsey wrote:

Doing this will cause errors on boot up, and the server will probably emit an alert tone.

I'm also not convinced about having software mirrors and hardware redundancy operating at the same time.

The previous post is a way of transferring data without having to reinstall or backup/restore to tape. Software mirroring was just a way to replicate a RAID 5 array to a single drive, the mirror would be broken afterwards of course. It requires you sit down and think about it until you are sure that at every stage you'll have a working server on at least one set of drives.

RE: SW mirroring some RAID controllers would let you do this too , but I had one incident where I had a RAID 5 array on disks 0,1,2 then added in Larger disks in 3,4,5 and mirrored the array with the intention of removing the smaller disks. When It had finished mirroring I had two RAID 5 arrays, one on 0,2,4 and the other on 1,3,5. Wonderful - each RAID 5 array had both large and small disks, [gosh, dearie me, my my (or words to that effect)] happily enough I had ordered a fourth large drive as a Hot spare ....

SW mirroring is not for long term use unless there is no possibility of HW redundancy. (SW raid 5 - scary - IIRC windows won't even boot from this)

I did say deep breath time , and no it ain't pretty. RAID 5 should be able to start up with one drive missing - if not then it's just stripping - yes you will get errors all over the place till you get back to a stable config - and yes I've had RAID 5 arrays trashed because a drive went off line and and the act of putting it on line caused the server to seem to synch the wrong drives (solution put that drive in a different slot , mark it as a hot spare, THEN it got rebuilt fine)