What is Synology Hybrid RAID
Synology Hybrid RAID (SHR) is a automated RAID management system from Synology, designed to meet the needs of easy deployment of a storage volume. If you do not even know what RAID is, this will be recommended setup for your storage volume on Synology NAS.
You will learn what different types of SHR exist and what their advantages/disadvantages over classic single disk/RAID setups are. In the end, you will be able to choose whichever type of RAID or SHR that is in the best interest of your storage volume. This article assumes that as the admin of your Synology NAS, you are also an experienced network administrator with a firm grasp of the RAID management.
The SHR is an automated RAID management system, designed to meet the needs of easy deployment of a storage volume. The SHR is designed to meet the needs for those users who do not care or do not want to know what are the finer aspects of the various RAID-levels which are currently supported on the Synology NAS, and would like to use the SHR to handle RAID management, storage expansion and maximize storage capability. The SHR allows for 1-disk or 2-disk worth of redundancy - meaning that the SHR Volume can suffer up to two disks lost, and the data volume will still be available for use. Note that a RAID volume (whether Classic RAID or SHR) is not a backup system.
Is SHR required?
No, it is not necessary to use the SHR. The SHR is based on a Linux RAID management system, and is completely optional to use. However SHR is strongly recommended for the novice user who has no technical background and still want the benefit of data protection on their storage. Using Classic RAID-levels is available for those users and administrators who understand the finer points of RAID technology and want to manage the RAID volume manually. The following manual RAID levels are available:
- RAID 0
- RAID 1
- RAID 5
- RAID 5+spare
- RAID 6
- RAID 10
How does the SHR maximize storage?
With Classic RAID, in the image towards the left, the storage volume is created based upon the smallest disk within the Array. As the Classic RAID Array was created with a 500GB drive, then all drives within that array can only use 500GB of space per hard drive, effectively creating a 5x500GB RAID Volume.
With the SHR, as reflected in the right image, the SHR will create divide each disk into smaller chunks, creating additional redundant storage, and allowing the capacity of each disks to be utilized to its maximum capacity.
Also with the SHR, if the storage system is being upgraded with larger disks - the newer storage will be available for use as soon as two disks have been upgraded, as there is enough drives to create a redundant storage array. With Classic RAID - the entire storage volume will have to be upgraded to all new drives before the new storage can be used, please refer to next section for further details.
Expanding with larger disks with SHR
When expanding drives within the Classic RAID, all disks must be updated to the newer drive capacity before the new storage pool can be utilized. With the Synology Hybrid RAID, given its ability of creating individual storage chunks in the storage array, allows newer storage to be utilized sooner. Accessing newer storage pool promptly becomes more prevalent with larger disks arrays, such as a 10-bay volume, reducing the immediate up-front cost of purchasing an entire set of drives to purchasing a drives over a period of time, upgrading storage as needed.
Synology Hybrid RAID with 2-Disk Redundancy
2-disk redundant version of the SHR is available since DSM 3.1. To use a 2-disk redundant SHR, the Volume will have to be created with a minimum of four drives. Note that converting from 1-disk redundant SHR to 2-disk redundant SHR is not available. When expanding a 2-disk redundant SHR Volume, whether by larger or additional disk, the new storage will be available as soon as 4-disks have been expanded or added into the SHR Volume.
When DSM's FTP service is enabled, you can turn your Synology NAS into a FTP server, allowing DSM users to access files on Synology NAS with a FTP application.
Can the SHR Volume be expanded with larger disks, such as 1TB to 3TB?
Yes, the SHR Volume can be expanded by incrementally changing out the disks one at a time, and allowing the DiskStation Manager to repair the volume. As soon as there is enough redundant storage available, the SHR will expand the usable storage capacity.
Can the SHR Volume be expanded with additional disks, such as 5x 1TB to 15x 1TB drives?
Yes, the SHR Volume can be expanded by adding additional disk to the existing array. This ability is available for those who are looking to expand their storage needs on an ad-hoc basis, where budget or storage needs require it.
Note that expanding a volume via this method can require a lot of time for the Synology NAS to expand to use all of the newly added drives. If possible, it's best to plan ahead of time and maximize the storage out during the deployment of the Synology NAS, as it's quicker to build a volume, versus expanding a volume via the addition of more disks.
Can the SHR Volume accept drives of smaller capacity once a SHR Volume has been created?
For clarification, if starting out with a SHR Volume utilizing 1TB drives, then all drives which are added or replaced to the SHR Volume must be equal or greater than 1TB. A 500GB drive cannot be added into an existing SHR (or Classic RAID) Volume, and have that storage pool of the smaller drive be utilized within the volume.