Synology DS420j Synology NAS Users Guide - Based on DSM 7.1 - Page 37

SSD Cache, Notes, Further reading

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Chapter 4: Storage & Virtualization Notes: Please note the following requirements and limitations: • The RAID type of the storage pool must have a fault tolerance of 1 or more drives (i.e., RAID 1, RAID 5, RAID 6, RAID 10, RAID F1, and SHR comprising at least two drives). • The capacity of the hot spare drive must be equal to or larger than the capacity of the smallest drive in a RAID 1, RAID 5, RAID 6, RAID 10, or RAID F1 storage pool. • The capacity of the hot spare drive must be larger than or equal to the capacity of the largest drive in an SHR storage pool. • HDDs and SSDs can each only be assigned as hot spares to storage pools of the same drive type. Only SSD hot spares can protect SSD storage pools, and only HDDs can protect HDD pools. SSD Cache SSD cache is a cost-effective way to improve the performance of HDD arrays. It improves random access by storing frequently accessed data on the SSDs of an SSD cache mounted on a volume or LUN. Note that this feature is only available on specific models. To find out which Synology NAS models support this feature, refer to this article. There are two types of SSD cache: • A read-only cache uses one or more SSDs to store frequently read data and accelerate random read performance. No data loss will occur in the event of SSD failure because this cache mode only stores copies of data from the volume. • A read-write cache uses at least two SSDs to create a fault-tolerant cache. The read-write cache first writes data to the SSDs to improve the random read/write performance and accelerate data access speed. Both types or modes of SSD cache can consist of up to 6 SSDs and must be comprised of drives of the same type. For more information on requirements and how to set up an SSD cache, refer to this article. If you are unsure what is the best SSD cache size for your use case, we strongly recommend running an analysis in Storage Manager > Storage > SSD Cache Advisor beforehand. The SSD Cache Advisor analyzes your current data use patterns and recommends a suitable SSD cache size for your selected volume. Allow the initial analysis to run for at least seven days for more accurate results. For more information about SSD Cache Advisor, refer to this article. Further reading You may want to read the following related articles for more information: • Important considerations when creating SSD cache • Frequently asked questions about using Synology SSD cache • What is the minimum recommended size for my SSD cache? 34

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34
Chapter 4: Storage & Virtualization
Notes:
Please note the following requirements and limitations:
• The RAID type of the storage pool must have a fault tolerance of 1 or more drives (i.e.,
RAID 1, RAID 5, RAID 6, RAID 10, RAID F1, and SHR comprising at least two drives).
• The capacity of the hot spare drive must be equal to or larger than the capacity of the
smallest drive in a RAID 1, RAID 5, RAID 6, RAID 10, or RAID F1 storage pool.
• The capacity of the hot spare drive must be larger than or equal to the capacity of the
largest drive in an SHR storage pool.
• HDDs and SSDs can each only be assigned as hot spares to storage pools of the same
drive type. Only SSD hot spares can protect SSD storage pools, and only HDDs can protect
HDD pools.
SSD Cache
SSD cache is a cost-effective way to improve the performance of HDD arrays. It improves
random access by storing frequently accessed data on the SSDs of an SSD cache mounted on
a volume or LUN. Note that this feature is only available on specific models. To find out which
Synology NAS models support this feature, refer to
this article
.
There are two types of SSD cache:
• A
read-only cache
uses one or more SSDs to store frequently read data and accelerate random
read performance. No data loss will occur in the event of SSD failure because this cache
mode only stores copies of data from the volume.
• A
read-write cache
uses at least two SSDs to create a fault-tolerant cache. The read-write cache
first writes data to the SSDs to improve the random read/write performance and accelerate
data access speed.
Both types or modes of SSD cache can consist of up to 6 SSDs and must be comprised of
drives of the same type. For more information on requirements and how to set up an SSD
cache, refer to
this article
.
If you are unsure what is the best SSD cache size for your use case, we strongly recommend
running an analysis in
Storage Manager
>
Storage
>
SSD Cache Advisor
beforehand.
The SSD Cache Advisor analyzes your current data use patterns and recommends a suitable
SSD cache size for your selected volume. Allow the initial analysis to run for at least seven days
for more accurate results.
For more information about SSD Cache Advisor, refer to
this article
.
Further reading
You may want to read the following related articles for more information:
•
Important considerations when creating SSD cache
•
Frequently asked questions about using Synology SSD cache
•
What is the minimum recommended size for my SSD cache?