The volume of generated and transmitted data is growing every year. On a Mac, it’s becoming more and more difficult to find free space for files, and in addition it is advisable to organize a backup, for which there is always not enough disk space.
RAID technology comes to the rescue, which can solve both data security issues and help with the speed of access to them.
What is a RAID array?
RAID technology ( Redundant Array of Independent Disks ) allows you to combine several physical drives into one logical drive to increase the reliability of data storage or increase system performance .
Previously, RAID was used on servers with a large amount of data or for the sake of additional protection. And today, such arrays are found in conventional technology for the people.
RAID can be configured on a home server or NAS. And an array of drives can even be assembled from old HDDs or several different drives inside one computer.
To understand which one is best for you, let’s look at several options for RAID arrays – they have different advantages and disadvantages. In the article I will mention the three most popular configuration options.
RAID 0: non-redundant array
This type of array consists of two or more drives. The copied data is divided into small parts and written to all disks at the same time.
The more disks will be combined in RAID 0, the greater the speed of writing and reading can be obtained. The increase in speed will be noticeable when working with large files on fairly powerful computers.
The main drawback of this specification is the decrease in reliability . Any file to be copied will be divided into parts that will be stored on all disks of the array. If one of the drives fails, all data will be lost. Recovering a file without parts that were stored on a failed drive will fail.
With an increase in the number of disks in a RAID 0 array, data processing speeds increase, but the likelihood of system failure increases.
RAID 1: mirrored array
Such an array also consists of two or more drives. At the same time, the file is not divided into parts when copying, but is written synchronously to each disk.
Roughly speaking, you will always have as many copies of each file as there are disks in RAID 1 .
Due to this, the reliability of the system increases significantly. RAID 1 will work and store data while at least one of the drives in the array remains operational. This is such a super-backup of computer data, many times protected from damage to any drive.
Cons: such an array does not give a gain in speed with data. The speed of writing and reading will be limited by the performance of the slowest of the system disks.
JBOD: merged array
This type of array is not RAID, but in fact it is a virtual disk, which consists of several smaller drives.
That is, you simply combine several different physical drives into one logical one. Instead of several disks, one will be as if common .
All the disks included in the JBOD summarize their size when working in this mode, but do not give the user a gain in data transfer speed and do not increase the reliability of information storage.
Cons: if one of the drives fails, all data is lost, as in RAID 0, and the transfer speed will be limited by the speed of the slowest drive in the system.
So what type of RAID array to choose?
RAID 0 is for those who want to increase read and write speeds for the system. This will be useful on computers with old drives, or on a Mac, which is used as a media server in the house. The array will provide quick access to files from multiple devices at once.
The volume of the array will be equal to the sum of the drives included in it.
RAID 1 is useful for those who do not use backup systems, but want to protect their data in case of physical damage. All files will be stored in at least two copies, and in case of failure of one of the disks will remain on the second.
Each disk does not increase the size of the array. RAID 1 of three 1TB drives will have the same volume – 1TB, but it will create two backups at once , in addition to the original file.
JBOD is best done when you need to get one large virtual drive from several small drives. For example, when using two 128 GB drives, you can get a JBOD with a capacity of 256 GB.
How to create a RAID array on macOS
- Launch Disk Utilityon Mac.
- In the menu bar, select File – RAID Assistant …
- In the window that opens, select the appropriate array type.
- Specify the drives on the Mac (some drives will need to be formatted first).
- Confirm the intention to create the array and wait for the process to complete.
Attention! All data from drives when creating arrays will be deleted.
How to migrate macOS to a RAID array
After creating the array, it will be displayed as a separate disk in the system and disk utility. In order to quickly transfer the working operating system to our array, you will have to use third-party applications – for example, Carbon Copy Cloner .
- Download the application from the developer’s siteand install it. The program is paid, but there is a 30-day trial.
- On the main screen, as the source ( the Source), select Mac system disk and specify the menu to copy all of the files.
- As destination ( Destination) we indicate our new RAID array.
- Press the Clonebutton and wait for the end of the process.
When all the data has been copied, get a full copy of your working system on the RAID array. You can boot and work with it.
On new Macs with a T2 chip, you will need to perform a series of manipulations to boot from an external drive.
What is the use of a RAID array in reality?
Thanks to RAID, on a Mac with multiple drives, you can expand the disk capacity, increase the speed of data access, or even do built-in mirroring instead of Time Machine backups .
Let me give you some basic, massive examples. An old MacBook, in which it is technically possible to install a second HDD or SSD , can earn faster when using a RAID 0 array.
Mac Pro with a pair of disks or Mac mini after the upgrade thanks to RAID 1 will receive an integrated backup system to protect this in case of damage to the drive.
Finally, a few small disks or flash drives and combine them into a JBOD for use as a “file trash”.
The main thing is that you generally have at least two disks to create a RAID array. And the rest is very simple.