General
For easy sharing and managing data on DiskStation, Synology DSM provides 3 types of volumes: SHR volume, single volume on RAID, and multiple volumes on RAID. SHR is the easy and fast way to create a volume (or a Disk Group); single volume on RAID is created directly on top of the selected hard disk(s) using all its/their space; while multiple volumes on RAID are created on top of a Disk Group composed of one to several hard disks, and you can expand the volume if there is still available space on the Disk Group.
When creating a volume/Disk Group, you have to choose a RAID type for them. Data protection in different levels may be provided according to the RAID type you choose when creating the volume/Disk Group. Synology DiskStation supports the following RAID types:
- Synology Hybrid RAID* (Quick mode): optimizes the space allocation of the volume/Disk Group when combining hard disks with different sizes. If a SHR volume/Disk Group is composed of 2 or 3 hard disks, data integrity is protected when any of the hard disk fails. If a SHR volume/Disk Group is composed of 4 or more hard disks, data integrity is protected when one or 2 of the hard disks fail.
- Basic: uses only one hard disk to create a volume/Disk Group that does not have any data protection mechanism.
- JBOD*: combines at least 2 hard disks to create a volume/Disk Group. The available capacity of the volume/Disk Group equals to the total capacity of all the member disks. JBOD allows combining hard disks with different sizes.
- RAID 0*: combines at least 2 hard disks to create a volume/Disk Group that does not have any data protection mechanism. If any of the member disks fails, the data in the volume/Disk Group is lost. The available capacity of the volume/Disk Group equals to the total capacity of all the member disks.
- RAID 1*: combines 2 - 4 hard disks to create a volume/Disk Group. The system will write identical data to each hard disk. Data integrity is protected when at least one disk is normal. The available capacity of the volume/Disk Group equals to the size of the smallest member disk.
- RAID 5*: combines at least 3 hard disks to create a volume/Disk Group and stripes both data and parity information across all the member disks. Therefore, when any disk fails, the system can be rebuilt by using the parity information on the other disks, so data integrity is protected. The available capacity of the volume/Disk Group = (capacity of the smallest hard disk) X (number of hard disks - 1)
- RAID 5+Spare*: combines at least 4 hard disks to create a volume/Disk Group. 1 disk will be used as the hot spare disk, and the other disks will be used to create a RAID 5 volume/Disk Group. When any disk of the RAID 5 volume/Disk Group fails, the hot spare disk will be added to the RAID 5 volume/Disk group automatically to ensure the data integrity. The available capacity of the volume/Disk Group = (capacity of the smallest hard disk) X (number of hard disks - 2)
- RAID 6*: combines at least 4 hard disks to create a volume/Disk Group and stripes both data and parity information across all the member disks. Therefore, even when 2 member disks fail, the system can be rebuilt by using the parity information on other disks, so data integrity is protected. The available capacity of the volume/Disk Group = (capacity of the smallest hard disk) X (number of hard disks - 2)
- RAID 10*: combines at least 4 hard disks to create a volume/Disk Group, and an even number of disks is required. RAID 10 has the performance of RAID 0 and provides data protection level of RAID 1. The available capacity of the volume/Disk Group = (capacity of the smallest hard disk) X (number of hard disks / 2)
Note:
- The volume types with "*" are only available for specific models according to the number of installed hard disks.
- Models which support hot spare do not support RAID 5+Spare.
You can choose to create different types of volumes according to your needs.
- SHR volume: It is created in Quick mode and provides the optimal space allocation and the possibility of future expansion by replacing or adding hard disks.
- Single volume on RAID: It is created using all the space of selected hard disks. The volume is created directly on top of hard disks. It provides the best access performance.
- Multiple volumes on RAID*: It is created on top of a Disk Group that is a collaboration of hard disks. You can create more than one volume on the Disk Group and expand volume size whenever in need. It provides the flexibility of dynamic capacity management. Multiple volumes on RAID can help you to set up the space quota for a specific use. For example, if you want to set up the quota for downloads as 50 GB, you can create a 50 GB volume on a Disk Group and create a shared folder on the volume only for downloading files. By that, you can limit the space of the shared folder.
A Disk Group is composed of one to several hard disks combined into different RAID level. This feature provides the following advantages:
- You can create as many volumes as needed on a Disk Group. The minimal size of a volume is 1 GB.
- You can specify the volume size according to your needs and expand it easily in DSM when there is still available space on the Disk Group without worrying about stopping the services.
Note:The feature is only available for Synology DiskStation with more than 2 bays.