SSD caching on Synology and Qnap – will it improve performance?

SSD caching on Synology and Qnap – will it improve performance?

Any advice on SSD caching? I’ve got 2 M.2 Sata SSDs installed in raid 0 (2 * 512GB Samsung 850 Evo) in my QM2 expansion card with 10GBE networking and I’m not getting the performance boost to commonly accessed files that i was expecting. I can see that data is being cached but not sure how to measure performance increase. I was also transferring files to my samsung 960 evo m.2 NVME SSD so there shouldn’t be a bottleneck there. I’m maxing out at around 350MB/s which was the same with the SSDs installed.

The objective of enabling SSD cache is to increase the performance of random access to a small portion of data that is frequently accessed in the storage space. For example, both large sequential read or write operations (e.g., HD video streaming) and entirely random data reading patterns lack re-reading patterns, and thus will not benefit significantly from SSD caching. For general applications, it is recommended to enable the Skip sequential I/O option, so that sequential I/O can still pass through to the drives of the storage space.

https://www.synology.com/en-uk/knowledgebase/DSM/help/DSM/StorageManager/genericssdcache

SSD Cache

SSD cache can improve the performance of random access by storing frequently accessed data on the SSD cache. SSD cache can be mounted on a volume or iSCSI LUN (Block-Level). There are two types of SSD cache:

  • Read-only cache can consist of 1 to 12 SSDs which can be mounted respectively in a basic or RAID 0 configuration to improve the random read performance of the storage space on which it is mounted.

    Note:SSD read-only cache stores copies of data from the volume; thus, no data loss will occur even if the read-only cache has crashed.

  • Read-write cache can be mounted in a RAID 1 / RAID 5 / RAID 6 configuration, depending on the number of SSDs (up to 12 SSDs), to improve the random read and write performance of the storage space on which it is mounted.

Both types of SSD cache implement an LRU (Least Recently Used) algorithm to swap the data in the cache.

How cache works on a NAS – (LRU and FIFO mode)

Synology ssd cache compatibility

 

SSD cache with additional card M2D18:

Built in NVMe
  • DS918+
  • DS1019+
 From 

Samsung SSD 970 EVO MZ-V7E250BW M.2 2280 NVMe 250GB SSD
Samsung SSD 970 EVO MZ-V7E500BW M.2 2280 NVMe 500GB SSD
Samsung SSD 970 EVO MZ-V7E1T0BW M.2 2280 NVMe 1TB SSD
Samsung SSD 970 EVO MZ-V7E2T0BW M.2 2280 NVMe 2TB SSD
M2D18 +NVMe & SATA SSD
  • FS1018
  • DS3018xs
  • RS2818RP+
  • RS2418(RP)+
  • DS1618+
 From 

Intel SSDPEKKA256G701 DC P3100 256GB M.2 NVMe SSD
Samsung MZ-V5P256BW 950 PRO 256GB M.2 NVMe SSD

Samsung MZ-V7P1T0 970 PRO 1TB M.2 NVMe SSD
Samsung MZ-V7P512 970 PRO 512GB M.2 NVMe SSD
Samsung MZ-V7E2T0 970 EVO 2TB M.2 NVMe SSD
Samsung MZ-V7E1T0 970 EVO 1TB M.2 NVMe SSD
Samsung MZ-V7E500 970 EVO 500GB M.2 NVMe SSD
Samsung MZ-V7E250 970 EVO 250GB M.2 NVMe SSD
Samsung MZ-V6E1T0 960 EVO 1TB M.2 NVMe SSD
Samsung MZ-V6E500 960 EVO 500GB M.2 NVMe SSD
Samsung MZ-V6E250 960 EVO 250GB M.2 NVMe SSD
Samsung MZ-V6E250BW 960 EVO 250GB M.2 NVMe SSD

Western Digital WDS100T2X0C Black 1TB M.2 NVMe SSD
Western Digital WDS500G2X0C Black 500GB M.2 NVMe SSD
Western Digital WDS256G1X0C Black 256GB M.2 NVMe SSD
Western Digital WDS250G2X0C Black 250GB M.2 NVMe SSD

Samsung SSD 970 EVO MZ-V7E250BW M.2 2280 NVMe 250GB SSD
Samsung SSD 970 EVO MZ-V7E500BW M.2 2280 NVMe 500GB SSD
Samsung SSD 970 EVO MZ-V7E1T0BW M.2 2280 NVMe 1TB SSD
Samsung SSD 970 EVO MZ-V7E2T0BW M.2 2280 NVMe 2TB SSD
M2D18 card +SATA SSD
  • FS2017
  • RS18017xs+
  • RS4017xs+
  • RS3617xs+
  • RS3617RPxs
  • RS3618xs
  • DS3617xs
  • RS1219+
  • RS818(RP)+
  • DS1817+
  • DS1517+
 From 

Crucial CT1050MX300SSD4 MX300 1TB M.2 SATA SSD
Crucial CT525MX300SSD4 MX300 525GB M.2 SATA SSD
Crucial CT275MX300SSD4 MX300 275GB M.2 SATA SSD
Kingston SUV500M8/480G UV500 480GB M.2 SATA SSD

Samsung MZ-N6E2T0 860 EVO 2TB M.2 SATA SSD
Samsung MZ-N6E1T0 860 EVO 1TB M.2 SATA SSD
Samsung MZ-N6E500 860 EVO 500GB M.2 SATA SSD
Samsung MZ-N6E250 860 EVO 250GB M.2 SATA SSD
Samsung MZ-N5E1T0 850 EVO 1TB M.2 SATA SSD
Samsung MZ-N5E500 850 EVO 500GB M.2 SATA SSD
Samsung MZ-N5E250 850 EVO 250GB M.2 SATA SSD

Western Digital WDS200T2B0B-00YS70 Blue 2TB M.2 SATA SSD
Western Digital WDS100T1B0B-00AS40 Blue 1TB M.2 SATA SSD
Western Digital WDS500G1B0B-00AS40 Blue 500GB M.2 SATA SSD
Western Digital WDS250G1B0B-00AS40 Blue 250GB M.2 SATA SSD

SSD– A Solid State Drive is a data storage device using integrated circuit assemblies as
memory to store data persistently. This enables a much faster transfer speed than
HDD.

HIT Rate– How often a searched-for item is actually found in the cache. The greater the number of
requests that can be served from the cache, the faster the overall system performance
becomes.

IOPS– Input / Output Operations Per Second, is a common performance measurement
used to benchmark computer storage devices.

 

SSD cache technology
QNAP solid-state drive (SSD) cache technology is based on disk I/O reading caches.
When the applications of the Turbo NAS access the hard drive(s), the data will be stored in
the SSD. When the same data are accessed by the applications again, they will be read
from the SSD cache instead of the hard drive(s). The commonly accessed data are stored
in the SSD cache. The hard drive(s) will only be accessed when the data could not be
found from the SSD.

 

QNAP SSD cache technology provides two algorithms:
(1)LRU (Default): Higher HIT rate, but requires more CPU resources.
When the cache is full, LRU discards the least-used items first. As the system needs to
track the cached data to ensure the algorithm always discards the least recently used
data, it requires more CPU resources but provides a higher Hit rate.
(2)FIFO: Requires less CPU resources, but lower HIT rate.
When the cache is full, FIFO discards the oldest data in cache. This reduces the HIT rate
but does not require too much CPU resources.

 

 

Applications and benefits
 Database: MySQL, MS SQL Server, etc.
 Virtual machine: VMware, Hyper-V, XenServer, etc

http://files.qnap.com/news/pressresource/product/SSDcache-whitepaper_en.pdf

 

 

Uncompromising performance for demanding applications

The SSD cache feature on QNAP NAS accelerates IOPS performance by up to 10 times and reduces latency by 3 times for storage volumes. It is perfect for IOPS-demanding applications including databases and virtualization to significantly improve overall workflow.

SSD cache volume varies with the size of RAM
Cache capacity RAM requirement
512GB ≧ 1GB
1TB ≧ 4GB
2TB ≧ 8GB
4TB ≧ 16GB

 

 

 

 

https://www.qnap.com/solution/ssd-cache/en/

 

SSD cache compatible NAS models

NAS Models SSD Cache Slot Supported SSD Cache Slot Number Remark
TDS-16489U All All
TES-x85U All All The rear SSD slots only support 2.5-inch SATA 6Gb/s drives
TVS-ECx80U-SAS All All This series also has 2 mSATA slots for caching.
TVS-ECx80U-SAS R2 All All This series also has 2 mSATA slots for caching.
TS/TVS-x79U-SAS All All
SS-x79U-SAS All All
TS-ECx80U Disk 1, 2, 3, 4 4 This series also has 2 mSATA slots for caching.
TS-ECx80U R2 Disk 1, 2, 3, 4 4 This series also has 2 mSATA slots for caching.
TS-ECx80 Pro Disk 5, 6, 7, 8 4 This series also has 2 mSATA slots for caching.
TVS-ECx80 Disk 5, 6, 7, 8 4 This series also has 2 mSATA slots for caching.
TS/TVS-x79U Disk 3, 4 2
TS/TVS-x79 Pro Disk 7, 8 2
TVS-882ST2, TVS-882ST3, TVS-882S All All
TVS-x82T TVS-682T/882T: SSD slot 1, 2
TVS-1282T: SSD slot 1, 2, 3, 4		 TVS-682T/882T: 2
TVS-1282T: 4		 This series also has 2 M.2 SATA III slots for caching.
TVS-x82 TVS-682/882: SSD slot 1, 2
TVS-1282: SSD slot 1, 2, 3, 4		 TVS-682/882: 2
TVS-1282: 4		 This series also has 2 M.2 SATA III slots for caching.
TS-x73U All All The built-in M.2 SSD slots are recommended for caching.
TVS-x73 All All This series also has 2 M.2 SATA III slots for caching.
TVS-x71 Disk 1, 2, 3, 4 4
TVS-x71U Disk 1, 2, 3, 4 4 This series also has 2 mSATA slots for caching.
TS-x70U Disk 3, 4 2
TS-x70 Last two trays 2
TS-x70 Pro Last two trays 2
TS-1635 Disk 1, 2, 3, 4 4
TS-x63U All All
TVS-x63 All All Disk slots 1 & 2 are recommended for caching.
TS-563 All All Disk slots 1 & 2 are recommended for caching.
TS-x51 All All
TS-453U All All
TS-453U-RP All All
TS-451U All All
TS-853U Disk 5, 6, 7, 8 4
TS-853U-RP Disk 5, 6, 7, 8 4
TS-1253U Disk 9, 10, 11, 12 4
TS-1253U-RP Disk 9, 10, 11, 12 4
TS-x53B All All The last two disk slots are recommended for caching.
TS-x53A All All Disk slots 3 and above are recommended for caching.
TS-x53 Pro All All
TS-x53S Pro All All
TS-531P All All Disk slots 1-4 are recommended for caching.
TS-x31+ All All
TS-x31X All All
TS-x31XU All All
TS-453mini Disk 1, 2 2
TS-453Bmini All All Disk slots 3 & 4 are recommended for caching.

Synology NAS list with M.2 SSD option:

Synology DiskStation NAS DS918+ 4-Bay (4GB RAM)

Synology FlashStation NAS FS1018 12-Bay 2.5″, 4x 1GbE, PCIe

Synology DiskStation NAS DS1817+ (2GB) 8-Bay, 4x 1GbE, PCIe

Synology DiskStation NAS DS1517+ (2GB) 5-Bay, 4x 1GbE, PCIe

Synology DiskStation NAS DS3018xs 6-Bay, 4x 1GbE, PCIe

Synology DiskStation NAS DS1517+ (8GB) 5-Bay, 4x 1GbE, PCIe

Synology DiskStation NAS DS1817+ (8GB) 8-Bay, 4x 1GbE, PCIe

Synology DiskStation NAS DS918+ (8GB) 4-Bay (8GB Synology RAM)

 

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