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I have a few questions on how software and onboard RAID 5 compare:

  1. Is there any way to add a disk to an existing RAID 5 array using either software or onboard RAID?

  2. All motherboards I'm interested in come with both SATA2 and SATA3 ports. Using either software or onboard RAID, is it possible to combine disks connected to different ports in the same array?

  3. If I have two operating systems installed (on a disk that does not belong to the array), can still use software RAID?

Notes:

  • I have read Onboard RAID vs Software RAID. It doesn't cover any of my questions.

  • I know that hardware RAID is better than both options. Sadly, I can't find a single RAID controller card. I've searched all over the country...

  • I know that RAID is not backup. Protecting my data from a single disk's failure is all I want.

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3 Answers 3

up vote 2 down vote accepted

Is there any way to add a disk to an existing RAID 5 array using either software or onboard RAID?

Depends on the OS version and onboard RAID vendor/version. For example, onboard RAID using Intel Rapid Storage Technology (any recent Intel chipset uses it), you can even convert RAID1 to RAID5 online. You can also add a disk to an existing RAID5 online too.

All motherboards I'm interested in come with both SATA2 and SATA3 ports. Using either software or onboard RAID, is it possible to combine disks connected to different ports in the same array

Most probably not. Usually, one chipset is RAID-based, and the other is not. For example, my motherboard has Intel ICH10 chipset and Marvell chipset. Intel RAID sees only disks connected to the Intel chipset.

Update: According to Intel, on the PCH controller hub (used in Intel P67), RAID5 with 5 or 6 drives is supported. However, be aware that all RAID features can be disabled by the board manufacturer.

If I have two operating systems installed (on a disk that does not belong to the array), can still use software RAID?

Depends on the OS. You cannot use Windows RAID in Linux and vice versa, but if these are two installations of Windows, why not?

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Regarding 2, all disks would be connected to the same chipset (Intel P67). Does this mean it should work? –  Dennis Oct 25 '11 at 21:41
    
Updated with specific info on P67. –  haimg Oct 25 '11 at 21:51
  1. It depends on the particular RAID software or hardware you're using. Most low-end controllers and software solutions do not support this.

  2. With software RAID, you should be able to combine ports regardless of what they're connected to. With onboard RAID, it usually depends on whether all the ports are connected to the same controller. This can vary from motherboard to motherboard.

  3. Yes, assuming the operating system has a driver that supports whatever software RAID method you're using.

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Regarding 3, do you know two software RAID programs (one for Windows 7, the other for Ubuntu 10.04) that are compatible? –  Dennis Oct 25 '11 at 21:42
    
The only ones I know of are ones where the Linux implementation was specifically designed to be compatible with the existing hardware and Windows implementations. For example, the driver for Intel southbridge 'hardware' RAID. However, you can RAID separately at partition level. (Make two partitions on each drive and RAID one pair in Linux and the other pair in Windows.) –  David Schwartz Oct 25 '11 at 21:46
    
Sadly, that's quite the opposite of what I had in mind. I'd like to keep the OSs on a disk that does not belong to the array and have a big "data" array that's accessible from all OSs... –  Dennis Oct 25 '11 at 22:51
    
You can do this with Intel chipset RAID. It's really software RAID, just supported in the BIOS so that you can boot from it. –  David Schwartz Oct 25 '11 at 23:13
  1. Depends on software/chipset. Better chances in software raid.
  2. Yes, using software raid. Probably not using onboard raid, depends on chipset.
  3. Yes. Just make sure not to touch the partition tables. Better setting up raided operating system last to avoid error-prone partitioning work after creating the raid.

You should be able to buy some RAID controller cards at all computer webshops I guess.

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Shipping things here is a mayor headache. They tend to get "lost". –  Dennis Oct 25 '11 at 21:39

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