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Changed lots of text and wording

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Joshua Boniface
2017-02-22 01:03:24 -05:00
parent 9f5fc95070
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@ -11,11 +11,9 @@ RAID protects you against one and only one thing: a disk failure.
It does _not_ protect you against any of the following things:
* Multiple disk failures beyond the RAID level chosen (e.g. both disks in a mirror, or 3 disks in a RAID-6), including possible [UREs](https://holtstrom.com/michael/blog/post/588/RAID-5-URE-Failures.html).
* Failure of the RAID controller itself (especially when using hardware RAID), the computer running the RAID, or the environment (a flood, fire, theft, etc.).
* Data corruption on-disk from filesystem bugs, cosmic rays, or minor hardware or firmware failures.
* Malicious or accidental deletion or modification of files by yourself or another party, including viruses, bad application writes, or administrative mistakes (e.g. `rm`-ing the wrong file or `mkfs` on an existing filesystem).
* Multiple disk failures beyond the RAID level chosen (e.g. both disks in a mirror, or 3 disks in a RAID-6), including possible [UREs](https://holtstrom.com/michael/blog/post/588/RAID-5-URE-Failures.html) - on that later subject, RAID-5 should be considered harmful these days for any disks larger than 1TB.
* Failure of the RAID controller itself (especially when using hardware RAID), the computer running the RAID, or the environment containing the servers (a flood, fire, theft, etc.).
* Data corruption on-disk from filesystem bugs, cosmic rays, or minor hardware or firmware failures, which can and do happen all the time - you usually just don't notice and software works around it.
* Malicious or accidental deletion or modification of files by yourself or another party, including viruses, bad application writes, or administrative mistakes (e.g. `rm`-ing the wrong file or `mkfs` on an existing filesystem), which any seasoned sysadmin has done at least once (and hopefully not to production data)!
The adage is simple: "RAID replicates _everything_, instantly, even the stuff you don't want." Like the deletion of a file or corruption.
For these reasons and more, RAID IS NOT A BACKUP!
The adage is simple: "RAID replicates _everything_, instantly, even the stuff you don't want it to."