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Ignorant Question about RAID 5

rustyrpage asked
Medium Priority
Last Modified: 2010-04-03
I have a RAID 5 array on my main file server.  It was 3 72.6gb 15k drives...I added another 72.6gb 15k drive in an effort to increase my capacity by another 72gb...however, when I put it in & use HP's configuration, I now have the same amount of space on the C: drive & in looking at the drive management, it shows that it is part of the RAID & an upartioned space on Disk 0.  

How do I get the 67.4gb of unallocated space to be added to my 135.66gb of space (of which only 11gb is free) without deleting ANY data off the 135.66gb?

Please help me, I know this is something simple & I am hoping that it is a process that doesn't take too long since downtime is bad.  (I could have sworn that I could just put the drive in, add it to the array & automatically have the data start striping accross it...too optimistic I guess!)

Thanks ahead of time.

Server:   HP Proliant ML370 w/SCSI
OS:        Windows 2000 Advanced Server SP4
RAM:      4gb

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Hi rustyrpage,

The C: drive refers to a partition on a disk, not the disk itself. So you need to resize the NTFS partition. Partition Magic has a good rep for this


There are also various free Linux based tools, but I suspect they might choke on a RAID.

Also, never forget that a raid is not and excuse to not back up your data! Before doing any risky operation, take a full backup.



Partition Magic won't do anything with a Window Server drive will it?  (last I tried)
Lee W, MVPTechnology and Business Process Advisor
Most Valuable Expert 2013

You cannot extend C: (The system or the boot drive).  You may be able to extend D: or other drives, but not C:.  Your RAID controller must support extending the logical RAID volume - if I'm reading what you said and interpreting it correctly, then yours does and I THINK it's already extended the logical volume.  BUT, the Windows Partitions can be extended using DISKPART - reference:
http://support.microsoft.com/?kbid=300415 (especially the info on "EXTEND").

You COULD try using thrid-party tools such as Partition Magic or Partition Commander to extend the C: drive, but this can be dangerous and it should NOT come as a shock to you if you end up corrupting the entire drive (it may work fine, but any time you mess with partitions like that you COULD cause serious damage, logically speaking (not physically).

I am unaware of any raid5 controller (consumer class) that has the capability to "expand" a raid5 set like you describe.    The typical way to do what you want is to rebuild the array- from scratch.

* Image backup of the array contents
* Wipe out raid config, build NEW raid config
* Image restore of array contents

And yeah, that translates to big downtime.

If someone finds otherwise (ability to "expand" raid5 set with this controller), I will be quite surprised...


My RAID controller is a smart array 641. (by HP).  I thought the purpose of doing RAID is to have this ability.
Lee W, MVPTechnology and Business Process Advisor
Most Valuable Expert 2013

Most Servers sold by Dell and HP and I suspect other major vendors offer the ability to dynamically increase RAID volume sizes as well as to convert from RAID 1 to 5.  They have been doing this, I would say, at least the past 2-3 years... possibly longer.


Well, let me ask this...if I just format this unallocated space into the D: drive (thus giving me a 62gb D: drive), my assumption would be that although it isn't part of the C: drive, it is still part of the RAID 5, thus giving me the redundancy I need/want, is that correct?
Lee W, MVPTechnology and Business Process Advisor
Most Valuable Expert 2013

Yes, that would be correct (Are you saying you never partitioned this - you made ONE BIG C: drive?  Ouch... not advisable on a server).
Technology and Business Process Advisor
Most Valuable Expert 2013
To amend that, if your SURE that disk is a part of the RAID 5 - for example, if you look in Disk Management and see ONE disk there with your C: drive and Unallocated or RAW space beyond the C drive, then YES, THAT WOULD BE CORRECT.

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There's only so much you can do when you come in to someone else's work.

I am thinking about buying 2 or 3 more of the same drive (bring me to a total of 5 or 6 72.6gb drives). Then I would leave the C: drive on the 136gb partition, then have an additional 136gb on the D: drive.  That seems like my safest & fastest bet (minimal down-time since I can do all of that while the server is running)
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