We're still running WIN XP Pro and recently purchased a 16TB RAID External Backup solution from Buffalo (it's a DriveStation™ Quad). It has four each 4TB drives currently configured in a RAID 10.

When plugged into the Windows machine, Disk Management is showing the Buffalo DriveStation Device as four separate drives as follows:

2048 GB

2048 GB

2048 GB

1306.58 GB

My question are:

  1. Does that sound right in terms of available space as Windows is reporting for a RAID 10? According to https://www.icc-usa.com/raid-calculator, we should have 8TB.

  2. Because Windows is reporting this device as four separate drives (due to the 2TB limit on 32 bit systems), how does Windows honor the array?

For example, if I start dumping files in Drive D, are those files automatically distributed to the other three drives in the array since the Device is configured for RAID 10 and had an internal controller?

I'm a little lost as how this works since due to the limitations of Windows XP (32 bit) with drives larger than 2TB, I don't have the luxury with working with a single 16TB drive letter where the RAID works silently behind the scenes.

migrated from stackoverflow.com Jul 21 '13 at 6:50

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  • You would rather lose 50% of your storage space the migrate to a newer operating system and GPT portions? – Ramhound Jul 21 '13 at 14:53

Three things:

1) Four 4TB drive in RAID 10 should indeed yield 8TB usable space.

Half of it is used as by the mirror/RAID1 part. RAID 1 is explained in simple terms in this post on SF.

2) If windows is reporting four separate drives then either:

  • Your DriveStation™ is not configured as RAID 10, or
  • Your DriveStation™ is presenting a single 8TB disk to windows and on that disk are four volumes/filesystems. (I suspect that this is the case).

3) A 32 bit OS has no problem with drives larger than 2TB because it is 32 bit.

However windows XP uses MBR by default which has a problem with disks larger than 2TB. You either need some way around this (e.g. GPT partitioning, or some other driver expansion for XP, or a modern OS.)

I realise that "use a modern OS" is not the answer you want, but XP is old. It was released in 2001 and its design was quite good for that time. However it is showing its age and you will keep running into problems like this is you try to use XP and modern hardware. Add to that that support for XP will stop on 8th of April 2014 and that you really should not use it after that since there will be no more security fixes. Combine these and migrating to a more modern OS and ignoring the XP problems at the same time might be an economical choice.

  • Thanks for your reply. I do plan on upgrading OS soon, but in the meantime, can you point me to some recommendations for GPT partitioning and/or XP driver expansion to make this work for the time being? Thanks. – goxmedia Jul 21 '13 at 15:48
  • Also, if my DriveStation™ is presenting a single 8TB disk to windows and on that disk are four volumes/filesystems, as I drop files onto one of these volumes, will the RAID distribute per RAID 10? – goxmedia Jul 21 '13 at 15:50
  • Yes. You can test that by writing a (large) file to a single volume and seeing all four drives become active. it should also show in diskmanagement (start, run, diskmgmt.msc) where it should show a single disk with four 'bar's representing partitions. – Hennes Jul 21 '13 at 16:18

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