Limitations Of Dirty Data Flush Number; Formatting The Dmlu In The Event Of A Drive Failure - Hitachi AMS2100 User Manual

Limitations of Dirty Data Flush Number

Formatting the DMLU in the Event of a Drive Failure

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Hitachi AMS 2000 Family Copy-on-Write SnapShot User Guide
This setting determines the number of times processing is executed
for flushing the dirty data in the cache to the drive at the same time.
This setting is effective when SnapShot is enabled. When all the LUs
in the array are created in the RAID group of RAID 1 or RAID 1+0
(SAS drives or the SAS (SED) drives configured and in the DP pool),
if this setting is enabled, the dirty data flush number is limited even
though SnapShot is enabled. When the dirty data flush number is
limited, the response time in I/O, which has a low load and high Read
rate, shortens. Note that, when TrueCopy or TCE are unlocked at the
same time, this setting is not effective.
See Setting the System Tuning Parameter
System Tuning Parameter
Data Flush Number Limit.
When the DMLU is in a RAID group or DP pool with RAID5 or RAID6
and a drive failure occurs on the RAID group or DP pool with no
redundancy, the data in the DMLU will be incomplete and unusable.
At that time, for the firmware version of 08C3/F and later, the DMLU
will automatically become unformatted, so make sure to format the
DMLU.
For less than 08C3/F, even though the DMLU will not automatically
become unformatted, make sure to format the DMLU.
It is possible to format a DMLU without having to release the DMLU.
Planning and design
or for CLI, see
for the setting method about the Duty
Setting the