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With "striping", a file's data blocks are distributed across different physical disks. In a simple RAID system (no protection), disk A would contain blocks 0, 2, 4, ..., and disk B would contain blocks 1, 3, 5, ... So if one disk fails, you lose everything. RAID5 uses n+1 disks to contain n disks worth of data, and so can recover from one disk failure. RAID6 uses n+2 disks to contain n disks worth of data, and so can recover from two disk failures.

With Stablebit's drive pool software, a file is written entirely on a single disk, but then that file is copied to a different physical disk in the pool so that the file exists in two places. So the drive pool uses 2*n disks to contain n disks worth of data (assuming all of the disks are the same size).

A RAID5 or RAID6 system uses fewer disks to store n disks worth of data than a drive pool. However, the drive pool allows you to unplug a single disk and connect it to a different computer and access all of the files on it (since it is a simple NTFS disk containing complete files); you cannot do that with a RAID disk (since each file is distributed over multiple disks).

With two 2TB disks in the pool, and file duplication for all files, you would have 2TB of usable space (effectively, the second drive becomes an image of the first).

-- from CyberSimian in the UK

<blockquote data-quote="CyberSimian" data-source="post: 1153113" data-attributes="member: 141969">With &quot;striping&quot;, a file's data blocks are distributed across different physical disks.&nbsp; In a simple RAID system (no protection), disk A would contain blocks 0, 2, 4, ..., and disk B would contain blocks 1, 3, 5, ...&nbsp; So if one disk fails, you lose everything.&nbsp; RAID5 uses n+1 disks to contain n disks worth of data, and so can recover from one disk failure.&nbsp; RAID6 uses n+2 disks to contain n disks worth of data, and so can recover from two disk failures.With Stablebit's drive pool software, a file is written entirely on a single disk, but then that file is copied to a different physical disk in the pool so that the file exists in two places.&nbsp; So the drive pool uses 2*n disks to contain n disks worth of data (assuming all of the disks are the same size).A RAID5 or RAID6 system uses fewer disks to store n disks worth of data than a drive pool.&nbsp; However, the drive pool allows you to unplug a single disk and connect it to a different computer and access all of the files on it (since it is a simple NTFS disk containing complete files); you cannot do that with a RAID disk (since each file is distributed over multiple disks).With two 2TB disks in the pool, and file duplication for all files, you would have 2TB of usable space (effectively, the second drive becomes an image of the first).-- from CyberSimian in the UK</blockquote>

[QUOTE="CyberSimian, post: 1153113, member: 141969"] With "striping", a file's data blocks are distributed across different physical disks. In a simple RAID system (no protection), disk A would contain blocks 0, 2, 4, ..., and disk B would contain blocks 1, 3, 5, ... So if one disk fails, you lose everything. RAID5 uses n+1 disks to contain n disks worth of data, and so can recover from one disk failure. RAID6 uses n+2 disks to contain n disks worth of data, and so can recover from two disk failures. With Stablebit's drive pool software, a file is written entirely on a single disk, but then that file is copied to a different physical disk in the pool so that the file exists in two places. So the drive pool uses 2*n disks to contain n disks worth of data (assuming all of the disks are the same size). A RAID5 or RAID6 system uses fewer disks to store n disks worth of data than a drive pool. However, the drive pool allows you to unplug a single disk and connect it to a different computer and access all of the files on it (since it is a simple NTFS disk containing complete files); you cannot do that with a RAID disk (since each file is distributed over multiple disks). With two 2TB disks in the pool, and file duplication for all files, you would have 2TB of usable space (effectively, the second drive becomes an image of the first). -- from CyberSimian in the UK [/QUOTE]