Raid 1

In this section we will discuss raid 1. We will will look at how this raid level can protect your data in the event that a disk fails.

Raid level 1 is the first step in disk redundancy. With raid level 1, two disks are mirrored. This means that what ever is written to one disk, is copied to the other. This process is automatic.

I refer to disk redundancy and not data redundancy. If a file is accidentally deleted on a raid level 1 file system, it's deleted on both disks, even though they are mirrored.

Take note of this. Raid one does not protect your data, it protects against hardware, or disk failure. If you lose one disk, the other is there so you can still access your data. Always make a backup.

With backups you can restore individual files in the event that something goes wrong, file level wise.

Typical raid level 1 setup. 2 disks mirrored
Raid 1

As you can see, raid level 1 is great for protecting against a disk failure.

So whats the cons. You need 2 disks. So, if you want to protect against a drive failure, you have to buy 2 disks. Cost is one downside to raid level 1.

Then there's also performance. You can only use 2 disks with a raid level 1 configuration. You also have to write the same data twice. Once to each disk. So, write performance is pretty bad.

When reading from a raid level 1 configuration, it's a different story. You see, when you read back from disk, half of the data can be read from one disk while the other half can be read from another disk. This could make reads twice as fast as a normal disk.

Some raid software allows you to set the read policy so that you can get maximum performance when reading from the disks.

Is raid level 1 actually useful? Well, yes, of course. Most operating systems are mirrored using raid level 1. Some vendors even build hardware raid controllers onto the motherboard to speed up writing to the disks.

Some of these on-board controllers even contain some cache, with battery backup. Perfect to mirror your operating system disks with.

Raid 1 can be configured with hardware or software raid.

Return from Raid 1 to Raid Levels

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