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Fixed markdown formatting

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Joshua Boniface 2016-09-28 12:25:10 -04:00
parent 4e33da3592
commit 112e622367
4 changed files with 11 additions and 11 deletions
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It is a common technique to provide _resiliency_ and _availability_ to a set of data and protect against one of the most common data loss scenarios: the failure of a disk.
It is a common technique to provide **resiliency** and **availability** to a set of data and protect against one of the most common data loss scenarios: the failure of a disk.
The simplest type of RAID is a 'mirror', which does just what it sounds like: keeps two (or more) copies of data on two (or more) different disks. If one disk fails, the second copy is still available and no data loss has occurred.

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Having a number of disks in RAID may _seem_ like a backup, especially if you're using a mirror mode. But this is *wrong*!
Having a number of disks in RAID may **seem** like a backup, especially if you're using a mirror mode. But this is **wrong**!
RAID protects you against one and only one thing: a disk failure. It does *not* protect you against any of the following things:
RAID protects you against one and only one thing: a disk failure. It does **not** protect you against any of the following things:
1. Multiple disk failures beyond the RAID level chosen (e.g. both disks in a mirror, or 3 disks in a RAID-6).
2. Failure of the RAID controller itself (especially when using hardware RAID), the computer itself, or the environment (a flood, or fire, perhaps).
@ -15,6 +15,6 @@ RAID protects you against one and only one thing: a disk failure. It does *not*
4. File corruption from bad writes or bit rot (except for ZFS), including whole-volume corruption from administrative mistakes (e.g. =mkfs= on an existing filesystem).
5. Malicious or accidental deletion or modification of data by yourself or another party, including viruses.
The adage is simple: "RAID replicates _everything_, even the stuff you don't want, like the deletion of that file you needed."
The adage is simple: "RAID replicates **everything**, even the stuff you don't want, like the deletion of that file you needed."
For these reasons and more, RAID IS NOT A BACKUP!

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1. Always back up in _some way_. While a copy of the data on the same array won't protect you against all problems, it will protect you against some.
2. A _backup on the same server_ is susceptable to the _same failures as the original data_ set (hardware failure, natural disasters, and the like).
3. A good rule of thumb is _three copies_ (the RAID is only one copy for this purpose): the _original_, one _onsite copy_, and one _offsite copy_. Store the offsite copy in the cloud, or at a friend's house.
4. _Make backups regularly_, at least once a week; the day you need a backup is the day you realize you hadn't run it in 6 months and what you need isn't backed up.
5. _Test backups regularly_, at least once a month; _a backup is worthless if you can't restore from it_. Just because you have a backup doesn't mean you're protected; always test them.
* Always back up in **some way**. While a copy of the data on the same array won't protect you against all problems, it will protect you against some.
* A **backup on the same server** is susceptable to the **same failures as the original data** set (hardware failure, natural disasters, and the like).
* A good rule of thumb is **three copies** (the RAID is only one copy for this purpose): the **original**, one **onsite copy**, and one **offsite copy**. Store the offsite copy in the cloud, or at a friend's house.
* **Make backups regularly**, at least once a week; the day you need a backup is the day you realize you hadn't run it in 6 months and what you need isn't backed up.
* **Test backups regularly**, at least once a month; **a backup is worthless if you can't restore from it**. Just because you have a backup doesn't mean you're protected; always test them.
There are dozens of backup utilities out there; I'm not going to prosthelytize for any one of them, but I personally use [BackupPC](http://backuppc.sourceforge.net/) for my server and workstation backups.

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@ -9,5 +9,5 @@ Now that you're in the know, get to making and checking a backup of your data, b
More information can be found on the following pages:
http://blog.open-e.com/why-raid-is-not-a-backup/
http://serverfault.com/questions/2888/why-is-raid-not-a-backup
* http://blog.open-e.com/why-raid-is-not-a-backup/
* http://serverfault.com/questions/2888/why-is-raid-not-a-backup