Extreme Cache
The Extreme Cache function uses PCIe Flash Modules (PFM) as the secondary cache to improve the read access
performance from the server.
Frequently accessed areas are written to the PFM asynchronously with I/O. When a read request is issued from
the server, data is read from the PFM to speed up the response.
Figure 25
Extreme Cache
PFM
ETERNUS DX
Controller
Read request
System memory
Disks
Frequently accessed
areas are written to
the PFM
When there is a read
request, the response
for the request will be
faster by reading data
from the PFM instead
of reading data from
the disks.
The PFM can be configured with different capacities in each slot of the controller enclosure.
The Extreme Cache function is enabled for read access to RAID groups that are assigned a controller that is in a
PFM installed controller enclosure. By allocating RAID groups with a high read access priority to a controller with
a larger PFM capacity, the read access performance is improved.
The assigned CMs for the RAID groups can be set by creating a RAID group manually or by changing the settings
in ETERNUS Web GUI or ETERNUS CLI after creation.
The Extreme Cache function can be enabled or disabled for each volume. Note that the Extreme Cache function
cannot be enabled for Deduplication/Compression Volumes, or volumes that are configured with SSDs.
Table 37
Maximum Number and Installable Capacity of PFMs
Item
ETERNUS DX500 S5/DX600 S5
ETERNUS DX900 S5
Maximum number of PFMs
(per ETERNUS DX)
8
16
PFM capacity
1.6TB, 3.2TB
For details on the maximum capacity that can be used as Extreme Cache, refer to
.
Caution
The Extreme Cache function may improve random I/O.
2. Basic Functions
Operations Optimization (Virtualization/Automated Storage Tiering)
72
Design Guide
Summary of Contents for ETERNUS DX S5 Series
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