Introduction to Coffer Disk

Latest reply: Nov 1, 2019 01:19:14 280 1 3 0

Coffer disk is used to temporarily store the raw data before they are actually written on the RAID. This is both a speed-up solution and a safety feature in the event of a blackout. To accomplish this task the coffer disks are helped by the BBU (backup battery unit). BBU unit is the backup battery that provides power to the storage controller to save all I/O into the coffer disk in the event of a power failure. Once the external power is restored, the cached data in the coffer disk will be flushed to the controller's cache an resume the I/O process to the physical disks in the external disk enclosures ensuring no data loss. Coffer disks are used to store three types of data: cache data requiring power failure protection, OceanStor OS system data, and system configuration information and logs.


The storage system has two kinds of coffer disks: built-in coffer disk and external coffer disk:

Built-in coffer disk
Each controller houses one or more disks as coffer disks inside. They can be mSATA or SSD disks.

External coffer disk
In case of external coffer disk we have to scenarios:

  • Disk and controller integration architecture

    If a storage system employs the disk and controller integration architecture, the first four disks in the storage system are configured as coffer disks. SAS, NL-SAS, or SSD disks can be used as coffer disks. The type of the four coffer disks must be the same. The coffer disks are labeled.



    Disk and controller integration architecture


  • Disk and controller separation architecture
    If a storage system employs the disk and controller separation architecture, the first four disks in the first disk enclosure are configured as coffer disks. SAS, NL-SAS, or SSD disks can be used as coffer disks. The type of the four coffer disks must be the same. The coffer disks are labeled.



    Disk and controller separation architecture


For the four disks, each spares an amount of space to form a RAID 1 group. The rest of the coffer disk space can be used to store service data.


If a coffer disk is removed or faulty, a "Coffer Disk Is Faulty" alarm is generated. You are advice to replace the coffer disk with one of the same capacity and type as other existing coffer disks.


Sources
https://support.huawei.com/enterprise/en/doc/EDOC1000138866/b5483573/coffer-disk
https://support.huawei.com/hedex/pages/EDOC1000182280YEG12274/14/EDOC1000182280YEG12274/14/resources/en-us_topic_0171110344.html

Forum cases
https://forum.huawei.com/enterprise/en/can-the-coffer-disk-be-interchangeable-with-other-hard-disks/thread/561423-891
https://forum.huawei.com/enterprise/en/are-the-coffer-disks-in-different-storage-devices-interchangeable/thread/561425-891

Knowledge Base
https://support.huawei.com/enterprise/en/knowledge/EKB1001299514
https://support.huawei.com/enterprise/en/knowledge/EKB1001268628
https://support.huawei.com/enterprise/en/knowledge/EKB1001292540
https://support.huawei.com/enterprise/en/knowledge/EKB1000401051

FAQ
https://forum.huawei.com/enterprise/en/corpus-14017.html
https://forum.huawei.com/enterprise/en/corpus-14014.html
https://forum.huawei.com/enterprise/en/corpus-13334.html

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little_fish
Admin Created Nov 1, 2019 01:19:14 Helpful(1) Helpful(1)

Very good, thanks.Introduction to Coffer Disk-3101224-1
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