Raid 5 explained

RAID is a giải pháp công nghệ that is used lớn increase the performance and/or reliability of data storage. The abbreviation stands for either Redundant Array of Independent Drives or Redundant Array of Inexpensive sầu Disks, which is older và less used. A RAID system consists of two or more drives working in parallel. These can be hard discs, but there is a trend lớn also use the giải pháp công nghệ for SSD (Solid State Drives). There are different RAID levels, each optimized for a specific situation. These are not standardized by an industry group or standardization committee. This explains why companies sometimes come up with their own chất lượng numbers and implementations. This article covers the following RAID levels:

The software to perkhung the RAID-functionality & control the drives can either be located on a separate controller card (a hardware RAID controller) or it can simply be a driver. Some versions of Windows, such as Windows Server 2012 as well as Mac OS X, include software RAID functionality. Hardware RAID controllers cost more than pure software, but they also offer better performance, especially with RAID 5 & 6.

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RAID-systems can be used with a number of interfaces, including SATA, SCSI, IDE, or FC (fiber channel.) There are systems that use SATA disks internally, but that have a FireWire or SCSI-interface for the host system.

Sometimes disks in a storage system are defined as JBOD, which stands for Just a Bunch Of Disks. This means that those disks bởi vì not use a specific RAID màn chơi và acts as stand-alone disks. This is often done for drives that contain swap files or spooling data.

Below is an overview of the most popular RAID levels:

RAID cấp độ 0 – Striping

In a RAID 0 system data are split up inlớn blocks that get written across all the drives in the array. By using multiple disks (at least 2) at the same time, this offers superior I/O performance. This performance can be enhanced further by using multiple controllers, ideally one controller per disk.


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RAID 0 – Striping

Advantages of RAID 0

RAID 0 offers great performance, both in read & write operations. There is no overhead caused by parity controls.All storage capathành phố is used, there is no overhead.The technology is easy lớn implement.

Disadvantages of RAID 0

RAID 0 is not fault-tolerant. If one drive fails, all data in the RAID 0 array are lost. It should not be used for mission-critical systems.

Igiảm giá khuyến mãi use

RAID 0 is ideal for non-critical storage of data that have sầu khổng lồ be read/written at a high speed, such as on an image retouching or Clip editing station.

If you want lớn use RAID 0 purely to lớn combine the storage capathành phố of twee drives in a single volume, consider mounting one drive sầu in the thư mục path of the other drive. This is supported in Linux, OS X as well as Windows & has the advantage that a single drive failure has no impact on the data of the second disk or SSD drive.

RAID màn chơi 1 – Mirroring

Data are stored twice by writing them lớn both the data drive sầu (or mix of data drives) & a mirror drive sầu (or phối of drives). If a drive sầu fails, the controller uses either the data drive or the mirror drive for data recovery and continuous operation. You need at least 2 drives for a RAID 1 array.


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RAID 1 – Mirroring

Advantages of RAID 1

RAID 1 offers excellent read tốc độ & a write-speed that is comparable to lớn that of a single drive sầu.In case a drive fails, data vày not have sầu khổng lồ be rebuild, they just have lớn be copied to the replacement drive sầu.RAID 1 is a very simple technology.

Disadvantages of RAID 1

The main disadvantage is that the effective storage capathành phố is only half of the total drive capathành phố because all data get written twice.Software RAID 1 solutions do not always allow a hot swap of a failed drive. That means the failed drive can only be replaced after powering down the computer it is attached khổng lồ. For servers that are used simultaneously by many people, this may not be acceptable. Such systems typically use hardware controllers that vì tư vấn hot swapping.

Ikhuyễn mãi giảm giá use

RAID-1 is ikhuyễn mãi giảm giá for mission critical storage, for instance for accounting systems. It is also suitable for small servers in which only two data drives will be used.

RAID màn chơi 5 – Striping with parity

RAID 5 is the most common secure RAID level. It requires at least 3 drives but can work with up to lớn 16. Data blocks are striped across the drives & on one drive sầu a parity checksum of all the bloông chồng data is written. The parity data are not written to a fixed drive, they are spread across all drives, as the drawing below shows. Using the parity data, the computer can recalculate the data of one of the other data blocks, should those data no longer be available. That means a RAID 5 array can withst& a single drive failure without losing data or access khổng lồ data. Although RAID 5 can be achieved in software, a hardware controller is recommended. Often extra cache memory is used on these controllers to lớn improve sầu the write performance.


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RAID 5 – Striping with parity

Advantages of RAID 5

Read data transactions are very fast while write data transactions are somewhat slower (due to lớn the parity that has to be calculated).If a drive sầu fails, you still have access khổng lồ all data, even while the failed drive sầu is being replaced & the storage controller rebuilds the data on the new drive sầu.

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Disadvantages of RAID 5

Drive failures have an effect on throughput, although this is still acceptable.This is complex công nghệ. If one of the disks in an array using 4TB disks fails và is replaced, restoring the data (the rebuild time) may take a day or longer, depending on the load on the array and the speed of the controller. If another disk goes bad during that time, data are lost forever.

Ikhuyễn mãi giảm giá use

RAID 5 is a good all-round system that combines efficient storage with excellent security và decent performance. It is igiảm giá for file & application servers that have a limited number of data drives.

RAID màn chơi 6 – Striping with double parity

RAID 6 is lượt thích RAID 5, but the parity data are written to lớn two drives. That means it requires at least 4 drives & can withst& 2 drives dying simultaneously. The chances that two drives break down at exactly the same moment are of course very small. However, if a drive sầu in a RAID 5 systems dies & is replaced by a new drive sầu, it takes hours or even more than a day lớn rebuild the swapped drive. If another drive sầu dies during that time, you still thất bại all of your data. With RAID 6, the RAID array will even survive that second failure.


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RAID 6 – Striping with double parity

Advantages of RAID 6

Like with RAID 5, read data transactions are very fast.If two drives fail, you still have sầu access lớn all data, even while the failed drives are being replaced. So RAID 6 is more secure than RAID 5.

Disadvantages of RAID 6

Write data transactions are slower than RAID 5 due lớn the additional parity data that have lớn be calculated. In one report I read the write performance was 20% lower.Drive failures have an effect on throughput, although this is still acceptable.This is complex giải pháp công nghệ. Rebuilding an array in which one drive failed can take a long time.

Igiảm giá khuyến mãi use

RAID 6 is a good all-round system that combines efficient storage with excellent security và decent performance. It is preferable over RAID 5 in tệp tin and application servers that use many large drives for data storage.

RAID màn chơi 10 – combining RAID 1 & RAID 0

It is possible khổng lồ combine the advantages (và disadvantages) of RAID 0 và RAID 1 in one single system. This is a nested or hybrid RAID configuration. It provides security by mirroring all data on secondary drives while using striping across each mix of drives to speed up data transfers.


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RAID 10 – Striping & mirroring

Advantages of RAID 10

If something goes wrong with one of the disks in a RAID 10 configuration, the rebuild time is very fast since all that is needed is copying all the data from the surviving mirror lớn a new drive sầu. This can take as little as 30 minutes for drives of 1 TB.

Disadvantages of RAID 10

Half of the storage capađô thị goes to lớn mirroring, so compared khổng lồ large RAID 5 or RAID 6 arrays, this is an expensive sầu way lớn have redundancy.

What about RAID levels 2, 3, 4 và 7?

These levels bởi vì exist but are not that comtháng (RAID 3 is essentially like RAID 5 but with the parity data always written khổng lồ the same drive). This is just a simple introduction to RAID-systems. You can find more in-depth information on the pages of Wikipedia or ACNC.

RAID is no substitute for back-ups!

All RAID levels except RAID 0 offer protection from a single drive sầu failure. A RAID 6 system even survives 2 disks dying simultaneously. For complete security, you bởi vì still need lớn back-up the data stored on a RAID system.

That back-up will come in handy if all drives fail simultaneously because of a power spike.It is a safeguard when the storage system gets stolen.Back-ups can be kept off-site at a different location. This can come in handy if a natural disaster or fire destroys your workplace.The most important reason lớn back-up multiple generations of data is user error. If someone accidentally deletes some important data and this goes unnoticed for several hours, days, or weeks, a good phối of back-ups ensure you can still retrieve sầu those files.

To learn more, read the page on the best back-up policy.


170 thoughts on “RAID”


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David S says:
January 28, 2021 at 12:45 am

My situation is as follows: trang chủ based technical speciamenu consultant. Work PC has an SSD (1.2TB Hãng sản xuất Intel 750 series PCIE 3.0) for C: drive & a SATA disk as my data drive sầu, which is backed up to lớn a 4-cất cánh NAS (Raid 5 IIRC), typically weekly in the past :(. Recently the original SATA disk (6TB WD Red, a bit less than 5 yrs old) failed with some loss of data. To my alarm, the replacement drive (10TB Exos) I added lasted just 9 days (hardware failure confirmed & now replaced by Exos supplier). I was intending to lớn replace my existing PSU (RM650) “just in case” but supplier was adamant that wasn’t necessary – just bad luchồng that the replacement failed. ??

For an *added* layer of protection, I am thinking of getting two new disks (10TB Exos, or possibly Surveillance AI ?) and setting them up in Raid 1 for D: drive. This is on the assumption it would provide a continuous duplicate copy of my data. The data would still be backed up to NAS of course. So in the event of one disk failing, there should be near zero loss of data (??).

My concern is that when I read up about Raid options, Raid 1 often seems to be not that favourably viewed.

To be clear:1. Shutting down the PC to lớn replace the failed drive sầu not a problem (its a single user PC)2. The cost of providing a second drive sầu for no increase in storage is not an issue. 10TB is well in excess of current needs, and the cost is minor relative sầu khổng lồ the potential cost of failure if have sầu only a single disk for D:. Even if no loss of data, recovery from NAS takes time, as does buying và setting up a new drive, etc. And even if only a few hours loss of data, reconstructing that can be time consuming.

Does the proposed arrangement make sense in my situation?Or should I be looking at other alternatives?