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RAID Problems

hckynt
hckynt asked
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Last Modified: 2016-12-08
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We have a Dell PE2850 w/ RAID 10 running SB Server 2003.  The server is suppose to have 4 73GB hard drives.  When I open Dell OpenManage Server Administrator it looks like the configuration is PERC4/Di (Embedded).  It also shows Channel 0 (RAID) - Backplace - Array Disks (which is where I can see all four drives) and then Channel 1 (SCSI).  What am I looking at?  How come I only have a single drive letter with 146GIG, instead of 292GiG?  Could someone please explain this to me?  Thanks!
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Lee W, MVPTechnology and Business Process Advisor
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Most Valuable Expert 2013

Commented:
No problem - this is as it should be - RAID combines drives so they appear larger and are redundant.  

RAID 10 means RAID 1+0 - 1 is a mirror - 0 is a strip.

You have two sets of two drives configured in a RAID 0, each set giving 146 GB total.  THEN you mirror them in a RAID 1 and because you are mirroring, you have an IDENTICAL COPY on the other 146 GB - you won't see 292 GB because you only have 146 GB of usable space.
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Top Expert 2012
Commented:
RAID10 is a mirror combined with striping.  Any mirror will leave you with half the total disk space.  See http://www.acnc.com/04_01_10.html

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Author

Commented:
Thanks for the quick response!

Three things...

1.  How come when I look at the Disk Management I don't see the mirror (I thought you used to be able to see the mirrors)?

2.  What would happen if I bought two more disks (the server holds 6)?

3.  When the server was setup, the primary partion was setup too small (in my humble opinion).  Is there a way to "move" space from the virtual drive to the logical drive?

Thanks for the help!
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Top Expert 2012

Commented:
1) The OS sees a RAID array as one volume, unless it is partitioned into more than one logical disk.

2) The rule of mirroring applies: you get only half of what you add, if they are the same size.

3) A tool like Partition Magic can help here.  Make sure you back everything up before messing around with the partition table.
Lee W, MVPTechnology and Business Process Advisor
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Most Valuable Expert 2013
Commented:
1.  It's a hardware mirror - the RAID controller MASKS the drives from the operating system and reports a "virtual disk" of sorts to the OS, only showing the OS what's available.

2.  You could create a RAID 0, 1, or JBOD with them.  RAID 0 IS NOT ADVISED EXCEPT when you can mirror them - which you already have.  A mirror would be your best bet (RAID 1).  JBOD - Just a Bunch of Disks - offers ZERO redundancy so don't store anything important on them.

3. How large is the primary C: partition - 12 GB is MORE than enough for 99% of the servers out there and is typically what Dell configures things with.  You should:
   a) move the Pagefile off the C: drive
   b) move the Exchange databases off the C: drive
   c) move SQL databases (if you have them) off the C: drive
   d) move the ClientApps folder off the C: drive

(That's the one thing I don't like about Dell - the preinstall SBS and put everything on the C: drive.
Lee W, MVPTechnology and Business Process Advisor
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Most Valuable Expert 2013

Commented:
2a - depending on the RAID controller it MIGHT be possible to convert to a RAID 5 on each RAID 0, then break the mirror and add the other disks to the RAID 5.  (Maybe break the mirror first). Then you would have 365GB of space (6x73-73) - RAID 5 does Number of Drives x size - 1 drive size = total space.

It MIGHT be necessary to kill the server and rebuild it if you want to convert RAID levels - depends on the controller (I'm not terribly familiar with the 4/Di, but I THINK it can dynamically adjust RAID volumes.

Author

Commented:
Thanks for all your help!

leew,
You called it exactly, the primary partion is only 12 GIG.  This is our DC and Exchange server.  Exchange was installed to the logical drive, as were all the other applications.  I also moved the user's directories off the primary partion.  However, SMSMSE and antivirus were installed to C:.  I have over 5 GIG left and I was just getting a little worried.
Lee W, MVPTechnology and Business Process Advisor
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Most Valuable Expert 2013

Commented:
Move the exchange databases off the C: drive and the page file as well.  There's little more than the occasional windows updates that you will or should need to install to C: so 5GB should be plenty.  

The process for Exchange 2003 should be essentially the same:
http://www.msexchange.org/tutorials/MF001.html
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