D-Link DSN-656 User Manual - Page 134

I/O Type, Write to HDD

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D-Link Document - User Manual The following steps describe details about a host read with a cache hit: 1. A host requests a read data. 2. Read data from the SSD. 3. Return requested data to the host. 4. If SSD has error, read data from the HDD.  Write Data The following figure shows the steps of the controller which handles a host write request. 1. Request Write 3. Return Status Memory Cache Data 4. Populate Cache 2. Write to HDD SSD HDD The following steps describe details about a host write: 1. A host requests a write data. 2. Write data to the HDD. 3. Return the status to the host. 4. Populate the cache to SSD. I/O Type The type of I/O access is a user-selectable SSD cache configuration. The user-selectable I/O type controls the SSD cache internal settings for cache block size, sub-block size, populate-on-read threshold, and populate-on-write threshold. Three pre-defined I/O types are supported; they are database, file system, and web service. The user can select an I/O type to set the SSD cache of a virtual disk. When SSD caching is enabled, the user can also change it online. But the cached data would be purged if the I/O type is changed. You may select the suitable I/O types depending on Copyright@2014 D-Link System, Inc. All Rights Reserved. 134

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D-Link Document – User Manual
The following steps describe details about a host read with a cache hit:
1.
A host requests a read data.
2.
Read data from the SSD.
3.
Return requested data to the host.
4.
If SSD has error, read data from the HDD.
Write Data
The following figure shows the steps of the controller which handles a host write request.
The following steps describe details about a host write:
1.
A host requests a write data.
2.
Write data to the HDD.
3.
Return the status to the host.
4.
Populate the cache to SSD.
I/O Type
The type of I/O access is a user-selectable SSD cache configuration. The user-selectable I/O type
controls the SSD cache internal settings for cache block size, sub-block size, populate-on-read
threshold, and populate-on-write threshold. Three pre-defined I/O types are supported; they are
database, file system, and web service. The user can select an I/O type to set the SSD cache of a
virtual disk. When SSD caching is enabled, the user can also change it online. But the cached data
would be purged if the I/O type is changed. You may select the suitable I/O types depending on
HDD
SSD
Memory Cache
Data
2. Write to HDD
4. Populate Cache
1. Request Write
3. Return Status
134
Copyright@2014 D-Link System, Inc. All Rights Reserved.