Extreme Cache Pool; Figure 27 Extreme Cache Pool - Fujitsu ETERNUS DX100 S4 Design Manual

2. Basic Functions
Operations Optimization (Virtualization/Automated Storage Tiering)
If the free capacity in the FTSP becomes insufficient while FTRP balancing is being performed,
•
an error occurs and the balancing session ends abnormally. Note that insufficient physical ca-
pacity cannot be replaced by other FTSPs.
When FTRP balancing is performed, an area for the work volume (the destination FTV which
•
has the same capacity as the source FTV) is secured in the FTRP to which the FTV belongs. As a
result, the status of the FTRP may temporarily become alarm status (the FTRP usage exceeds
the "Caution" or "Warning" threshold). This alarm state is removed once balancing completes
successfully.
• If the capacity of the FTRP is expanded during an FTRP balancing process, the balancing level
might be less than before.
• FTRP balancing may not be performed regardless of what FTRP balancing level is used. FTRP
balancing availability depends on the physical allocation status of FTVs.

Extreme Cache Pool

The Extreme Cache Pool function uses SSDs in enclosures as the secondary cache to improve the
read access performance from the server. Self Encrypting SSDs can be used in addition to SSDs.
Frequently accessed areas are written asynchronously to specified SSDs for Extreme Cache Pools.
When a read request is issued from the server, data is read from the faster SSD to speed up the
response.

Figure 27 Extreme Cache Pool

When there is a
read request, the
response for the
request will be
faster by reading
data from the SSDs
instead of reading
data from the disks.
• For the ETERNUS DX100 S4/DX200 S4
The maximum capacity that can be used as an Extreme Cache Pool is 800GB for each controller.
Specify one or two SSDs to be used for each controller.
400GB SSDs (MLC SSDs) can be used for Extreme Cache Pools. Value SSDs cannot be used.
To specify two SSDs per controller, the controller firmware version must be V10L82 or later,
and "Extreme Cache Pool (Expanded)" must be enabled.
A RAID group (RAID0) that is dedicated to the Extreme Cache Pool is configured with the speci-
fied SSDs, and volumes for the Extreme Cache Pool are crated in the RAID group.
Fujitsu Storage ETERNUS DX100 S4/DX200 S4, ETERNUS DX100 S3/DX200 S3 Hybrid Storage Systems Design Guide (Basic)
Read request
Cache memory
Extreme Cache Pool (SSDs)
54
Copyright 2023 Fujitsu Limited
ETERNUS DX
Controller
Disks
Frequently
accessed areas are
written to the
Extreme Cache
Pool (SSDs)
P3AM-7642-32ENZ0