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On 9 Feb 2010, at 15:43, Neil Bothwick wrote: |
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> On Tue, 9 Feb 2010 15:11:14 +0000, Stroller wrote: |
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> |
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>> You cannot remove one disk from the array and repartition it, because |
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>> the partition is across the array, not the disk. The single disk, |
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>> removed from a RAID 5 (specified by Paul Hartman) array does not |
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>> contain any partitions, just one stripe of them. |
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> |
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> A 3 disk RAID 5 array can handle one disk failing. Although |
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> information |
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> is striped across all three disks, any two are enough to retrieve it. |
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> |
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> If this were not the case, it would be called AID 5. |
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Of course you can REMOVE this disk. |
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However, in hardware RAID you cannot do anything USEFUL to the single |
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disk. |
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In hardware RAID it is the controller card which manages the arrays |
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and consolidates them for the o/s. You attach three drives to a |
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hardware RAID controller, setup a RAID5 array and then the controller |
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exports the array to the operating system as a block device (e.g. /dev/ |
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sda). You then run fdisk on this virtual disk and create the |
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partitions. You cannot connect just a partition to a hardware RAID |
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controller. |
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Thus in hardware RAID there are no partitions on each single disk, |
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only (as I said before) stripes of the partitions. You cannot usefully |
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repartition a single hard-drive from a hardware RAID set - anything |
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you do to that single drive will be wiped out when you re-add it to |
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the array and the current state of the virtual disk is propagated on |
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to it. |
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I hope this explanation makes sense. |
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I was not aware that Linux software RAID behaved differently. See |
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Joost's explanation of 9 February 2010 15:27:32 GMT. I asked if you |
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were referring to LVM because I set that up several years ago, and it |
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also allows you to add partitions as PVs. I can see how it would be |
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useful to add just a partition to a RAID array, and it's great that |
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you can do this in software RAID. |
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So this: |
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On 9 Feb 2010, at 00:27, Neil Bothwick wrote: |
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> With the RAID, you could fail one disk, repartition, re-add it, |
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> rinse and |
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> repeat. But that doesn't take care of the time issue |
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only applies in the specific case that Paul Hartman is using Linux |
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software RAID, not the general case of RAID in general. |
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Stroller. |
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