RAID explained

RAID explained

RAID (redundant array of independent disks) provides a way of storing the same data in different places on multiple hard disks (though not all RAID levels provide redundancy). By placing data on multiple disks, input/output (I/O) operations can overlap in a balanced way, improving performance. Since multiple disks increase the mean time between failures (MTBF), storing data redundantly also increases fault tolerance.

All 2 or more bay NAS devices and all internal/external RAID drives use some kind of raid setup.  This article explains the common RAID configurations used.

RAID 0 – Striping

Data is stored only once between two or more disks, usually used to increases performance. Minimal 2 disks are needed for RAID 0. Although this is supported by most of the NAS systems, we don’t usually promote this solution as it doesn’t give fault tolerance. This means even though any a single disk failed, you’ll lose all data. Storage capacity is equal to the total of both disks.


RAID 1 – Mirroring

Data is duplicated onto multiple disks, which gives 100% redundancy (most reliable).  RAID 1 does give a slight performance decrease.  Minimal 2 disks are needed for RAID 1, and total storage capacity will be half of total capacity of the disks.


RAID 3 – Striping with parity information

RAID 3 is RAID 1 (striping) combined with an additional disk to store recovery (parity) information. This means that if one of the data disks fail, the additional disk that contains the parity information can be used to rebuild data onto a new disk. Minimal 3 disks are needed. Considerable performance increase.



RAID 5 is by far the most common RAID configuration for business servers and enterprise NAS devices. This RAID level provides better performance than mirroring as well as fault tolerance. With RAID 5, data and parity (which is additional data used for recovery) are striped across three or more disks. If a disk gets an error or starts to fail, data is recreated from this distributed data and parity block— seamlessly and automatically. Essentially, the system is still operational even when one disk kicks the bucket and until you can replace the failed drive. Another benefit of RAID 5 is that it allows many NAS and server drives to be “hot-swappable” meaning in case a drive in the array fails, that drive can be swapped with a new drive without shutting down the server or NAS and without having to interrupt users who may be accessing the server or NAS.

Minimal 3 drives needed, and storage is 2/3rd of the total storage installed.

Synology SHR

Synology SHR is Synology answer to the (for some people) complex management of RAID. Synology Hybrid RAID (SHR) is an automated RAID management system, designed to make storage volume deployment quick and easy. If you don’t know much about RAID, SHR is recommended to set up the storage volume on your Synology NAS.


Do you need help with setting up your NAS – let me know via the contact form and I see if I can assist 😉 

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