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Rebuilding RAID

Occasional Advisor

Rebuilding RAID



We have a HP Server with 8 HDDs of 900 GBs each. One Harddisk is configured as RAID-0 and the other 7 are RAID-5. Windows 2008 OS is installed on RAID-0 which is not recommended and secure for OS as far as we know.


Is it possible to change RAID-0 to RAID-1+0 or any other recommended RAID Level for operating system but keep the RAID-5 intact in our server?


Secondly, as we don't have a spare hard disk to add it in RAID-0 to make it RAID-1+0, is it also possible to remove one of the hard disks from RAID-5 and add it in RAID-0? Will RAID-5 still work with 6 HDDs?


Any Suggestions?



Frequent Advisor

Re: Rebuilding RAID

If I recall the HP tool that is included when you use there smartstart cd to install the os does allow for the migration of RAID level. It's called HP Array Configuration and Diagnostic or ACD.


FYI - RAID 0 uses 2 hard drives and if the HP ACD tools allow for the migration then you're pretty much set.

I would clone the RAID-0 using clonezilla first before attempting this. I would also go a step further and test the clone you just made of the original system on a test server.

Frequent Advisor

Re: Rebuilding RAID

I think you're screwed.

I used smartstart 8.70 and what ever version of ACD I have installed doesn't allow for RAID-0 to be converted to RAID-1.

I have a Smart Array 410i RAID controller.


Honored Contributor

Re: Rebuilding RAID

Yes you can change the RAID level on-line. In Smart Array Terms, it's called RAID level migration.


No, you can not remove a disk from an Array.


The tool to you is called Array Configuration Utility (ACU).


There's som terms you need to know and understand:

Array, Logical drive, Expand and extend.

There's no standard, so each vendor, use their terms the way they like.

There's 2 tools for configuring the Smart Array controller (SA).

ACU, for the advanced features. And ORCA (Option ROM Configuable Adapter), simple and easy.


When you use the ACU to configure the SA, you must create 1 or more arrays.

When you create an array, you simply tell the SA, that these physical disks is grouped. You have not defined any RAID level yet. You can create several arrays, on the smart array controller.

Once you have createt an array, you can create logical drives. You can create several logical drives, of different RAID levels within an array. Ei. if you got 4 pcs 250 GB disks. You can create a 50 GB RAID 1 on disk 0 and 1, and a 50 Gb RAID 1 on disk 2 and 3, leaving 200 GB free disk space on each disk, on this free space you can create a 600 GB RAID 5.


You can add more disks to an array, it's called expand the array. If you add more disks, you will get some free space. With that free space you can add more LD's or you can extend LD's (make them larger).


Using yhe ORCA for creating arrays, you simply tell the SA use disk 0 and 1, and create a RAID 1 (On the SA, HP call it 1+0, but using 2 disks for a 1+0, give you a RAID 1). It will create a RAID 1, using the entire disk space = 1 LD per array. 


You can not schrink a LD. Nor can you remove disks from an array.


If you want to do a RAID level migration, you must have sufficient free space for the new RAID level.

If you got 1 disk, you can have RAID 0 only. If you want to get a RAID 1, you must add 1 more disk to the array, and then do a RAID level migration.


In you case, you got 2 disk's in a RAID 0. If you LD's use less than 50% you can do a migration. If your LD use more than 50%, then you must add 2 more disks.


There's a greate document aboute the SA, called: HP Smart Array technology brief.

And see if you can find a user guide for the ACU as well.








Occasional Advisor

Re: Rebuilding RAID

"FYI - RAID 0 uses 2 hard drives"

HP ACU is showing only one drive for my Raid-0 configuration where the OS is installed. That means RAID-0 can be created with a single drive.

Occasional Advisor

Re: Rebuilding RAID

OK Thanks. Is it possible to create a single 5 TB RAID-5 array with 6 Hard Disks of 900GB each?


Re: Rebuilding RAID

True RAID 0 requires at least 2 drives as your spanning data across drives. With 1 drive your really just setting up JBOD, but ACU still calls it RAID 1+0

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Frequent Advisor

Re: Rebuilding RAID

create share wrote:
OK Thanks. Is it possible to create a single 5 TB RAID-5 array with 6 Hard Disks of 900GB each?


It would be 4.5 TB, but yes that is possible.


The issue is you can't shrink a 7 drive 5.4TB array down to 6 drives. You would have to make a backup (disk image) of the volume on the array, delete the array and create it again in your desired configuration. This will involve downtime and you also need to worry about shrinking the partition -- make sure that not only your disk imaging utillity allows for this, but the disk utilization allows for it (i.e. if your RAID 5 parititions currently have 5 TB of data -- not possible without deleting files)


Also, slightly off topic, but highly relevant. I strongly advise you use a hot spare in RAID-5 and you read and understand the implications discussed here: