Power - Asus DS300j G2 Series User Manual

• Set the redundancy type to Active-Active.
See "Making Subsystem Settings (CLU)" on page <?>.
• Enable LUN Affinity and ALUA.
See "Making Controller Settings (CLU)" on page <?>.
For more information, see "Appendix C: Multipathing on Linux" on page <?>.
c P
ache olIcy
As it is used with ASUS DS300f G2, the term cache refers to any of several kinds of high-speed, volatile memory
that hold data moving from your computer to the physical drives or vice-versa. Cache is important because it can
read and write data much faster than a physical drive. There are read caches, which hold data as it is read from
a physical drive; and write caches, which hold data as it is written to a physical drive.
In order to tune the cache for best performance in different applications, user-adjustable settings are provided.
Cache settings are made on the RAID controller. See "Making Controller Settings (CLU)" on page <?>.
r c P
eAd Ache olicy
• Read Cache – The read cache is enabled but no pre-fetch action.
• Read Ahead – The read cache and predictive pre-fetch feature are enabled. Read-ahead anticipates the
next read and performs it before the request is made. Can increase read performance.
• Forced Read Ahead – The read cache and aggressive pre-fetch feature are enabled. See "Forced Read-
Ahead Cache" below.
• No Cache – The read cache is disabled.
w c P
rite Ache olicy
• Write Back – Data is written first to the cache, then to the logical drive. Better performance. ASUS DS300f
G2 has a cache backup battery to protect data in the cache from a sudden power failure.
• Adaptive Writeback – See "Adaptive Writeback Cache" below.
• Write Thru – Also "Write Through." Data is written to the cache and the logical drive at the same time. Safer.
If your write cache policy is set to Write Back, the write policy automatically changes to Write Thru when all of
the following conditions occur:
• The logical drive write policy is set to Write Back
• The Adaptive Writeback Cache feature is enabled
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• The cache backup battery goes offline
When the battery comes back online, the write policy automatically changes back to Write Back.
f r -A c
orced eAd heAd Ache
On the ASUS DS300f G2 subsystem, you can set the logical drive read cache policy to Forced Read Ahead an
enable the aggressive pre-fetch feature.
The Forced Read-Ahead cache policy setting provides predictive pre-fetching of data requests, allowing the
controller to aggressively buffer large chunks of data in cache memory to prevent frame drops on high-bandwidth
video playback. Not normally enabled for non-video applications.
A w c
dAPtive ritebAck Ache
On the ASUS DS300f G2 subsystem, you can set the logical drive write cache policy to Write Thru or Write Back.
If you set the write cache policy to Write Back, your data is first written to the controller cache, and later to the
logical drive. This action improves performance. To preserve the data in the cache in the event of a power failure,
the subsystem has a backup battery that powers the cache. To see an estimate of how long the battery can power
the cache, see "Viewing Battery Information" on page 89 or "Viewing Battery Information" on page 222.
The Adaptive Writeback Cache feature protects your data by changing the write cache settings while the cache
backup battery is offline. When all of the following conditions occur:
• The logical drive write policy is set to Write Back.
• The Adaptive Writeback Cache feature is enabled.
• The cache backup battery goes offline.
The write policy automatically changes to Write Thru. When the battery comes back online, the write policy
automatically changes back to Write Back.
To enable the Adaptive Writeback Cache option, see "Making Controller Settings (CLU)" on page <?>.
h c f
ost Ache lushing
On the ASUS DS300f G2 subsystem, you can enable or disable host cache flushing.
When enabled, host cache flushing guards against data loss in the event of a power failure. However RAID
performance is slightly reduced.
When disabled, the ASUS DS300f G2 subsystem has greater sustained bandwidth and lower latency, which are
helpful for real-time video capture.
When you operate the ASUS DS300f G2 with host cache flushing disabled, use a UPS to protect against data
DS300f G2 Series User Manual