I recently had someone perplexed by the fact that although two 512GB SSD disks have interconnected, it only sees a single disk for storage space. He may not know what 2x 512GB NVME SSD with RAID 1 on the web server and what this storage architecture entails.
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If you are novice in administering storage spaces on a server or on a simple computer, in this tutorial you will learn about NVME and what RAID entails. Let's take it one at a time and see why out of two interconnected disks you only see the storage space except on one.
What does this mean NVMe (Non-Volatile Memory Express)?
NVMe comes from (Non-Volatile Memory Express) and is a protocol for interconnection of storage devices such as SSDtheSolid State Drives) or flash storage modules (USB Stick, Memory Stick). This protocol is specially designed to exploit the high performance of flash -based storage devices and is mainly used for high performance storage devices. Most often they are used in server web architecture or database storage system. Where high writing / reading speed is required.
Different from traditional storage interfaces, such as SATA, NVME uses a connection PCI Express (PCIe) to allow faster data transfers between the calculation system and the storage devices. Nvme also uses an architecture of the type "queueing"Which allows several reading and writing operations to be processed simultaneously, which leads to increased performance and efficiency of the storage system.
What does this mean 2x 512GB NVMe SSD cu RAID 1?
Here is the so -called problem from which you see only one storage space. Although at a simple calculation made by a novice, two disk512GB, would mean a total of 1TB free space for storage.
In the case of servers web, the safety of stored data is very important. That's why disks are used SSD Interconnected NVME with RAID software 1. If a motherboard, memory or even CPU can be replaced without data loss, if a disk defects, the effects can be catastrophic.
What does Raid 1 mean?
RAID (Redundant Array of Independent Disks) is a software / data storage technology that combines multiple physical disks to achieve better performance and safety. It is a kind of binder of physical storage units that are interconnected in a system.
Several types of raid are available, which are molded in the requirements of each configuration. In the case of web servers, the best and most profitable choice is RAID 1.
What does 2x nvme ssd mean with raid 1?
RAID 1 is “Data mirror” from a disk. Mirroring. The data are duplicated on two identical discs, which ensures redundancy and if one of the discs are damaged, the data is still available on the other disk. Thus the data are protected in the case of a damage. Performed reading is improved, but writing performance is easily affected.
For web servers, data protection and reading speed are the top features of a disk. Therefore, 2x NVMe SSD With RAID 1 it is a good choice for web servers, where reading speed is more important than writing speed. Yes, it can be a disadvantage when the cache systems are chosen, but REDIS, memcached And others, I use cache on the RAM. (Another discussion).
If you want, Raid 1 helps create some kind of backup disk. This does not mean that if you have accidentally erased data from Disk, with RAID 1 you will be able to recover from the other disk. It is only about if one of the disks are damaged.
In conclusion, it is normal for the discs in a raid set to be seen by the operating system as a single disc. In the case of one RAID 1, the data are replication on both discs in the set, so the available space will only be equal to the space of a single disc, but the data will be redundant and secure if one of the disc has a failure.
Custom made: “df -h” Executed in a server with Linux, it will only display the storage space mounted / partitioned and currently used on each file system. If the partitions on the second disk are not mounted in the file system, then they will not be displayed as a result of the order. To check the available discs and existing partitions, you can use the order: fdisk -l or lsblk.
In conclusion, if on a server or computer you have two SSD NVME disks with RAID 1, you will not have available for storage than a volume equal to a single disk.
