RAID 0, 1, 2, 5, 6, 10 and SHR – differences & amp; Comparison (simply stated)

The term RAID appears mainly at the server or NAS server. We tell you the differences between RAID 0, 1, 2, 5, 6, 10 and Synology SHR. In addition, we will tell you why a RAID is not a backup and what the main differences between a software and a hardware RAID are.

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Imagine that you have a (NAS) server with multiple disks on which all your photos, videos and music from your childhood and your family are saved until now. Suddenly a hard drive fails, and all your memories are lost. That is an emotional disaster. Better it would be if the server would be secured so that the data is still available or recoverable if one or even be several disks - Welcome to RAID!

  • Setting up NAS server: goes like this&# 8217; s (manual)

What is RAID?

The abbreviation stands for RAID &# 8220;Redundant Array of Independet Disks&# 8221; in German loosely translated: &# 8220; Duplicate data on a separate hard drives network.&# 8221;

As an an example:

  1. You have a RAID system with four hard drives (Array of Disks), stored on the very important files.
  2. A hard disk fails or is stolen.
  3. Then you can install a new hard drive and the RAID system, the lost files, restore (Independent). Why?
  4. Because more information in the RAID system saved than necessary (redundant). With this information, a lost hard drive to be restored (at least) - RAID fifth

There are several types of RAID, which are characterized by their number. But what do they mean? To easily understand how the different RAID types work, we have prepared examples with hard disks that are always great every 4 TB. In a network with different sized hard drives, the result may be different.

If you want to see yourself as a RAID would look like if their various hard drive installs, then you can use this RAID calculator.

RAID 0

Reliability: NO

Available space: 100%

Example: With RAID 0, the hard drives are simply hung in a row. If you for example have a server with 2 x 4 TB hard drives, RAID 0 is the operating system from a hard drive with 8 TB. However, you have it no resiliency. When a hard drive breaks down, all data is lost on both disks.

RAID 0 is added to the memory of all installed hard disks to a hard drive.RAID 0 is added to the memory of all installed hard disks to a hard drive. Source: Synology

Conclusion: RAID 0 is suitable if you want to compile disks to build a large network and it does not matter if the data is lost it. Such RAID example can serve as a backup from another RAID. Why RAID is not a backup yourself, you read below.

RAID 1

Reliability: One or more hard drives

Available space:  50% (or less)

Example: You have a server with 2 x 4 TB hard drives (2-bay server). If RAID 1 is activated, the first hard drive is mirrored to the second. Now, if one disk fails, the data is still available on the other. However, you have in the example then only half of the built-in storage capacity - that is 4 TB.

If you have 4 x 4 TB hard drives (4-bay server) and RAID 1 is set, you can also just the space of a hard disk use (4 TB), since the other three disks are each copies. The space yield is then only 25%. but it could turn out three disks simultaneously and the data would still be available.

RAID 1 mirrors the first hard drive to any other installed hard disks.RAID 1 mirrors the first hard drive to any other installed hard disks. Source: Synology.

Conclusion: RAID 1 is particularly suitable for small 2-bay servers where you have a reliability of a hard drive. However, if you need large amounts of memory, the memory can very quickly become small. Because you have to buy quite a large hard drives from the outset to have a high storage efficiency. Only an 8-TB hard drive *RAID 0, 1, 2, 5, 6, 10 and SHR - differences & amp; Comparison (simply stated) currently costs around 350 euros.

RAID 5

Reliability: 1 hard drive

Available space:  66% (or more)

Example: RAID 5 only works on a server with three hard drives. Suppose you have a 3 x 4-TB disks: Then uses RAID 5, the storage capacity of a hard disk (4 TB) for recovery. The other two hard drives (8 TB) can use it.

If you have 4 x 4 TB hard drives, is also the storage capacity of a hard drive is not available. but you can use a total of three hard drives (12 TB).

RAID 5 always requires a hard drive as reliability.RAID 5 always requires a hard drive as reliability. Source: Synology

Conclusion: RAID 5 is especially suitable for 4-bay server with three or more disks. Here you have a very good memory yield, but also a maximum of only one hard disk can fail. The more hard drives do you use (6-Bay servers and higher) in addition, the riskier it is RAID. 5

RAID 6

Reliability: 2 hard drives

Available space:  50% (or more)

Example: RAID 6 works from a server with 4 hard drives. Suppose you have a server with 4 x 4 TB hard drives with RAID 6, then you can use two hard disks as storage (8 TB), the other two are used for reliability. It can turn out up to two hard disks and the data is still available (recoverable). If you had 6 x 4 TB hard drives, you could use four hard drives and two could fail simultaneously again.

RAID 6 always requires two hard drives as reliability.RAID 6 always requires two hard drives as reliability. Source: Synology

Conclusion: RAID 6 thus functions similarly to RAID 5, except that always two disks are used as a recovery storage. It is suitable from 4-bay server and beyond.

RAID 10

Reliability: 2 hard drives (or more)

Available space:  50%

Example: RAID 10 requires at least four hard drives. RAID 10 is a RAID 0, RAID composed of a plurality. 1 As with RAID 1 you have shown up only half of the total storage capacity available, no matter how many additional drives uses it. However, more may then characterized fail.

RAID 10 always supplies only 50% of capacity, but high reliability.RAID 10 always supplies only 50% of capacity, but high reliability. Source: Synology

Conclusion: RAID 10 with many disks, more than two drives can fail. This type primarily offers increased security and a fairly rapid recovery. This RAID type is used particularly in the professional environment.

SHR

The manufacturer Synology offers NAS server for home and professional use. Here, you can also use the proprietary SHR (Synology Hybrid RAID).

Reliability: 1 hard drive

Available space:  At least 50% (automatically adjusts to)

SHR is a good choice for hard disks of varying sizes.Compare: SHR provides more available space at hard drives of different sizes. Source: Synology

Conclusion:  Who privately no great desire to constantly figure out the optimal RAID system and adjust who can use SHR. This is always the most space is provided at a reliability of at least one hard drive as a function of the hard drive. It is particularly advantageous SHR when their hard drives of different sizes used together.

A RAID is NOT a backup

If ye set up, for example, a Synology NAS server with RAID, you might think:

Since a hard disk can fail, the whole system's backup. Then I need my data no longer even to secure extra!

Unfortunately, this is not correct. After a backup is a copy of your data that is ideally in a different place - that is a snapshot of a particular data set. A NAS server you have permanently working like an ordinary drive. RAID protects against the failure of one or more hard drives - right - but only on Hardware level!

So if a hard disk has a technical defect, you can exchange them. But what if a Software defect exists in the RAID system, thereby all data is stored wrong, but her only notice when it is too late? Then the RAID array is useless because the data indeed destroyed were written to the hard disk even if the hard drives themselves are functioning properly.

Conclusion: A RAID with reliability is a fine thing. But who wants to be sure to regularly create an additional backup of his important data - such as every month on an external hard drive or another, small NAS server with RAID 0th

Software RAID vs. Hardware RAID

The above description refers primarily to the available space. It is above all in the professional environment also depends on performance and fast recovery times. Here a software RAID different from a hardware RAID.

Software RAIDHardware RAID
costslowhigh
powerlowhigh
CPU load (host)highlow

Hardware RAID is generally more expensive, but offers high performance. In addition, the computational load in the respective HOST is lower. Hardware RAID also has the advantage that it is platform independent.

Conclusion: Hardware RAID is especially useful for professionals or companies. For Home is true when software RAID.

14.11.2017

Posted In: server

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