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SuperStorage SSG-1129P-ACR10N4L User's Manual
When the following screen appears, select Yes to confirm that the selected device is to be
used as a journaling drive. The options are
Yes
and No.
Note:
RAID Write Hole (RWH) is a condition associated with a power/drive-failure/crash
while writing to a RAID5 volume. The use of journaling drive that contains partial parity
logging (PPL) can reduce the potential data loss. Refer to the following illustration for
the use of journaling drive.
Disk1
Journaling
Drive
(Data)
Disk2
(Data)
Disk3
(Data)
Disk4
(Parity)
RAID SW for Read-modify-write Case
(PPL)
Partial parity logging (PPL) = old data XOR old parity
New parity = new data XOR PPL
(read) old parity
XOR operation
(write) new parity
Store PPL to the journaling drive
(read) old data
XOR operation
(write) new data
