Huawei OceanStor 2000 V3 Series Features Manual page 26

OceanStor V3 Series
HyperMetro Feature Guide for Block
Figure 1-2 Write I/O process
Host
Storage
1.
2.
3.
4.
5.
6.
Read I/O Process
Data on the LUNs of both storage systems is synchronized in real time and both are accessible
to hosts. If the storage system in one data center malfunctions, the storage system in the other
data center continues providing host services alone.
Issue 05 (2018-01-30)
2
DCL
LOG
6
Local storage array
An application host delivers a write I/O to the HyperMetro management module.
A log is recorded.
HyperMetro writes the write I/O to both the local and remote caches concurrently.
The local and remote caches return the write I/O result to HyperMetro.
A storage system returns the write I/O result to the application host after receiving
feedback from the local and remote caches.
The storage system determines whether dual-write is successful.
– If the write I/O request is processed successfully, the log is deleted.
– If the write I/O fails to be written to the local or remote cache, the log is converted
into a DCL. The DCL records the differential data between the local and remote
LUNs.
NOTE
If the write I/O fails to be written to the local or remote cache, HyperMetro services are
suspended and the storage system in each data center sends an arbitration request to the
quorum server. The storage system that wins the arbitration continues providing services and
the one that fails stops. In the background, the storage system uses the DCL to synchronize
data. Once the data on the local LUN is identical to the data on the remote LUN,
HyperMetro services are restored.
The DCL is stored on all the disks in the disk domain and four-disk RAID 1 is used for data
protection while storage system logs are stored on coffer disks.
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HyperMetro management module
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Local
cache
DWDM
Same-city network
Local
between data centers
LUN
1 Feature Description
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Remote
cache
Remote
LUN
Remote storage array
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