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I have a few 2-terabyte external drives i'm looking to introduce into our backup plan. I was wondering if i would gain anything out of partitioning the drives into 2-1-terabyte partitions and mirroring the two partitions on one drive? Does the drive become physically more reliable if it is partitioned into smaller parts? I'm assuming that if two identical hdd are dropped or exposed to harmful conditions that both drives will become equally corrupt regardless of the partitions.

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Micheal, could you please elaborate a bit more? – A Dwarf Jul 13 '11 at 13:51
up vote 3 down vote accepted

Note that the partition only exists logically. Physically, you're still using one drive, which is as prone to errors as every other drive would be.


  • You will be safe against accidental deletion of files on one partition in case the other one is not touched. Consider for example having the drive attached to a computer and deleting one file from one partition. It is unlikely you'll do the same thing on another partition.
  • You will be (somehow) safe against a slowly appearing hard disk failure. Once you notice sectors on the drive going bad, you may be lucky and get the data off from the other partition, but only because it's on another physical location on the platter(s)!


  • Writing twice as much data in each step wears the drive out faster than usual
  • You will not get the same write speed if you do the mirroring in-place.
  • You need to make sure the mirror is really 1:1 (check for synchronization!)
  • Sudden hard disk failures will mean that your data is gone. Having it mirrored on the drive is not going to be useful if the drive is mechanically dead or has other serious read errors.

To sum it up, what you want to do only helps you to prevent accidental deletions from an application/user layer. From a physical layer, you'd probably be better off using one drive with one partition.

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Thanks. I assumed this was the case but thought it would be interesting to hear it from someone else. I'll stick with no partition and relay on verification for creeping bad sectors and such. – Michael J. Lee Jul 13 '11 at 14:19
How is this magical RAID with one drive files safe from accidental deletion its a mirror? – squarebear Jul 13 '11 at 14:22
@Steve The question was edited after I answered. It's only safe if there is no constant mirroring involved, for example when you only mirror the drive while backing up, using software. – slhck Jul 13 '11 at 14:37
Also, nobody mentioned "RAID" :) – slhck Jul 13 '11 at 14:39
@Michael On reflection the question doesn't mention raid only mirror, however I've taken this to mean RAID1, fell a bit silly now, apologies – squarebear Jul 13 '11 at 14:42

From what I gather, you want to setup RAID 1 on two partitions? I wouldn't recommend it, because you will slow down your disk. Consider this: if you write a file to the disk, you would have to write it to both partitions. The head would move back and forth between the two partitions until the entire file is written to both partitions. This is A LOT of overhead.

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I seriously doubt that any software or hardware RAID would even allow it. The point of RAID1 is two drives, not partitions, with the same data. They would almost certainly not even give you the option to select two partitions on the same drive.

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Sorry but if your talking about setting up a raid1 on the same disk, it has no value what so ever all your doing is wearing the disk out twice as fast, it has no redundancy when the drive dies your backup is on the disk that is already dead, It doesn't provide anymore protection for accidental deletion that one partition because your deletion is mirrored across both partitions,

I don't no whether any partition software would let you setup a RAID on the same disk, REDUNDANT ARRAY OF INDEPENDENT DISKS,

sorry if i sound angry i get like that sometimes (I'm smiling inside :))

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