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24 BladeSymphony 1000 Architecture White Paper www.hitachi.com
For example, in Configuration 1 the shaded BANK 4 is a spare bank. Assume that the memory
correctable errors occur frequently in a memory on BANK 3. BIOS, which keeps counting the memory
correctable errors on each bank, activates the online copy function automatically upon the incidence of
the fourth error. All of the data on BANK 3 is copied to spare BANK 4. At the same time, a log is
recorded explaining that the data is copied to the spare bank, and the system displays a message
when the online sparing is complete, at which time the system operates with BANK1, BANK2, and
BANK4 (12 GB), the same capacity as before the online spare memory operation occurred.
Memory Mirroring
Mirroring the memory provides a level of redundancy that enables the system to continue operating
without the going down in case of a memory fault (including a plural-bits error).
Figure 15. Memory mirroring
When operating in normal conditions, data first writes in the primary (slots 1, 2, 5, and 6), then in the
mirror (slots 3, 4, 7, and 8). The arrows in Figure 15 show the relationship between the mirroring source
and the destination. When data is read out, it is read out of either the primary or mirror.
No memory testing of the mirror is carried out when the system is booted up after the mirroring is set.
Accordingly, only half of the total capacity of the memory installed is displayed both in the memory test
screen shown when the system is booted and in the total memory capacity shown when the system is
running.
Configuration 7 2 GB 2 GB
2 GB 2 GB None None None None
Configuration 8 1 GB 1 GB
1 GB 1 GB None None None None
Configuration 9 512
MB
512
MB
512 MB 512
MB
None None None None
Configuration
10
256
MB
256
MB
256 MB 256
MB
None None None None
Table 5: Online spare memory supported configurations
Bank Bank1 Bank2 Bank3 Bank4