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So lately I've been playing around with my recently purchased (used server) (HP ProLiant ML330 G6) and I am a bit confused as to the current RAID configuration it has. I did a bit of checking via the HP System Management webpage on my server and noticed the following, which in turn leads me to believe it is a RAID 10 configuration, as per the Smart Array controller.

enter image description here

To confirm, I have 4 slots with 4 x 1TB drives in there. In the screenshot above it clearly states 1+0.

From what I understand, RAID 10 is a stripe of mirrors as per the image below.

enter image description here

So if the data is distributed and mirrored across all disks(as per the image above), then why do I see 2 x Logical disks in my system with 1TB each? Why don't I just see 2TB total in 1 single logical drive, as per the image above?

EDIT

Additional Drive information as per request..

enter image description here

enter image description here

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    Probably because that's how RAID-10 is typically implemented. Does the OS see two drives, or just one? – womble Sep 28 '15 at 5:31
  • Yes, the OS detects 2 logical drives as per the Disk Management console. – Master Mick Sep 28 '15 at 6:29
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    Because someone created two Logical Drives. – ewwhite Sep 28 '15 at 6:33
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In HP-speak, Arrays are the physical grouping of disks. Logical Drives are a subset of the Array and present the actual block device to your OS.

You can have multiple Logical Drives within an array. Those Logical Drives can have different RAID levels as well.

For example, this is a group of 6 disks with two logical drives, each of RAID 1+0 (RAID10):

  array A (SAS, Unused Space: 1857528  MB)

  logicaldrive 1 (72.0 GB, RAID 1+0, OK)
  logicaldrive 2 (1.5 TB, RAID 1+0, OK)

  physicaldrive 1I:2:1 (port 1I:box 2:bay 1, SAS, 900.1 GB, OK)
  physicaldrive 1I:2:2 (port 1I:box 2:bay 2, SAS, 900.1 GB, OK)
  physicaldrive 1I:2:3 (port 1I:box 2:bay 3, SAS, 900.1 GB, OK)
  physicaldrive 1I:2:4 (port 1I:box 2:bay 4, SAS, 900.1 GB, OK)
  physicaldrive 2I:2:5 (port 2I:box 2:bay 5, SAS, 900.1 GB, OK)
  physicaldrive 2I:2:6 (port 2I:box 2:bay 6, SAS, 900.1 GB, OK)

But I could also do something like (note the RAID5 Logical Drive):

  array A (SAS, Unused Space: 2534  MB)

  logicaldrive 1 (72.0 GB, RAID 1+0, OK)
  logicaldrive 2 (1024.0 GB, RAID 1+0, OK)
  logicaldrive 3 (869.1 GB, RAID 5, OK)

  physicaldrive 1I:2:1 (port 1I:box 2:bay 1, SAS, 900.1 GB, OK)
  physicaldrive 1I:2:2 (port 1I:box 2:bay 2, SAS, 900.1 GB, OK)
  physicaldrive 1I:2:3 (port 1I:box 2:bay 3, SAS, 900.1 GB, OK)
  physicaldrive 1I:2:4 (port 1I:box 2:bay 4, SAS, 900.1 GB, OK)

So in your case, we're missing information... namely the sizes of the logical drives.

But from here, you have an Array of 4 disks, and two Logical Drives of unknown size carved out from that array.

  • Added more drive informaton showing logical, primary and sizes. Does that look like a RAID 1 setup? – Master Mick Sep 28 '15 at 7:52
  • It's exactly what I said. Someone created two logical drives of 1TB each on a group of four disks. – ewwhite Sep 28 '15 at 12:09
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HP Smart Array controllers (and any other recent raid implementation actually) treat raid1 as sort of raid10, which is exactly what they indicate. Raid10 is indeed a stripe of mirrors, but the trick is that mirror on two drives can also use striped reads at least - suppose you need to read two blocks - on block can be read from one drive, and another from second (on a consistent array, of course). That's what +0 indicates.

  • Naw, HP Smart Array controllers treat RAID1 as RAID1. See the creation options: [raid=0|1|1adm|1+0|1+0adm|5|50|6|60|?] - RAID1 is only available for arrays of two drives. Four or more are designated as RAID 1+0 when a logical drive is created. – ewwhite Sep 28 '15 at 12:49
  • Naw, it doesn't. I saw 1+0 configurations with two drives only. – drookie Sep 28 '15 at 12:53
  • HP documentation: [raid=] The raid parameter sets the raid level of the logical drive. If not specified, the default raid is the highest level possible. The availability of certain raid settings depends on the number of drives designated in the "drives=" parameter. For example, RAID 1 will only be available if two drives are selected while RAID 1+0 will be shown for a selection of 4 or more drives. – ewwhite Sep 28 '15 at 13:15
  • Largely depends on the firmware generation. You can google a bit and see same question several time appears on the forums and mailing lists - "why and how did I get 1+0 from two drives only". – drookie Sep 28 '15 at 13:27

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