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I've a dedicated server with an raid array with two disks of 1TB each, this is what I get with mdadm --detail /dev/md1

    Version : 1.1
Creation Time : Wed Aug  1 20:20:14 2012
Raid Level : raid1
Array Size : 975186812 (930.01 GiB 998.59 GB)
Used Dev Size : 975186812 (930.01 GiB 998.59 GB)
Raid Devices : 2
Total Devices : 2
Persistence : Superblock is persistent

Intent Bitmap : Internal

Update Time : Sat Aug  4 00:50:31 2012
      State : active 
Active Devices : 2
Working Devices : 2
Failed Devices : 0
Spare Devices : 0

       Name : xxxxxxxxxxxxx
       UUID : xxxxxxxxxxxxx
     Events : 4843

Number   Major   Minor   RaidDevice State
   0       8        3        0      active sync   /dev/sda3
   1       8       19        1      active sync   /dev/sdb3`

But I see the array with only 1TB and not the 2TB of both disks.

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closed as not constructive by John Gardeniers, womble, Scott Pack, Tim Brigham, Ward Aug 24 '12 at 3:50

As it currently stands, this question is not a good fit for our Q&A format. We expect answers to be supported by facts, references, or expertise, but this question will likely solicit debate, arguments, polling, or extended discussion. If you feel that this question can be improved and possibly reopened, visit the help center for guidance.If this question can be reworded to fit the rules in the help center, please edit the question.

Is this serious? – MDMarra Aug 3 '12 at 23:16
Sorry I've never used linux before, how should I know this? – Shixons Aug 3 '12 at 23:18
Yes. Because it is not Linux specific. RAID1 (or RAID5/6) setup of discs is very common in servers and both allow the server to keep operating if a disc has failed. This is essential to most corporate servers. A single disc failure should not result in problems for potentially hundred of people. And in reverse, how RAID and how backups work it something each admin should know. (Sorry if I sound harsh) – Hennes Aug 3 '12 at 23:21
Yes but I'm not a server admin, I'm just a webmaster with a high traffic website wich need a dedicated server. – Shixons Aug 3 '12 at 23:23
@Shixons: If you're not a sysadmin, this isn't the right site for you. As per the FAQ, Server Fault is a community for professional systems administrators. – womble Aug 4 '12 at 5:30
up vote 6 down vote accepted

From your post: Raid Level : raid1.

Two 1TB drives in a RAID 1 are supposed to yield 1TB of usable space. Everything is working as expected.

Think of your hard disks as books. To prevent loss of information (e.g. in case of a coffee spill) you write all your information to two books. Now your have two books but still only room for one book of entries.

For a bit more professional and a much longer answer check out this post: SF: Canonical question: What are the different widely used RAID levels and when should I consider them?.

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Thank you, I understand now. – Shixons Aug 3 '12 at 23:18

RAID1 is mirroring. You're only going to get the usable capacity of one disk.

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