172
Planning, Installing, and Managing the IBM System x3950 M2
– WThru: In Writethrough mode, the controller sends a data transfer
completion signal to the host when the disk subsystem has received all the
data in a transaction.
Set a check mark for the following setting if you want the controller to use
Writeback mode but the controller has no BBU or the BBU is bad:
Use wthru for failure or missing battery
If you do not set this option, the controller firmware automatically switches
to Writethrough mode if it detects a bad or missing BBU.
Disk Cache:
NoChange
is the default
The settings are:
– Enable: Enable the disk cache.
– Disable: Disable the disk cache.
– NoChange: Do not change the current disk cache policy.
I/O:
Direct
is the default
The I/O policy applies to reads on a specific virtual disk. It does not affect the
read ahead cache. The settings are:
– Direct: In direct I/O mode, reads are not buffered in cache memory. Data is
transferred to the cache and the host concurrently. If the same data block
is read again, it comes from cache memory. This is the default.
– Cached: In cached I/O mode, all reads are buffered in cache memory.
Disable BGI:
No
is the default
Specify the background initialization (BGI) status. A setting of
No
means that a
new configuration can be initialized in the background.
Physical drive and Migration panel
Options are shown in Figure 3-64 on page 173.
Tip:
A setting of
Yes
, disables BGI. Changing this setting is not
recommended because the controller is blocked while any outstanding
background process have to be completed, before further actions are
allowed.
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