Disk Caching
The following parameters are supported only by clusters of version 9.1.0 or later.
enable_disk_cache
Parameter description: Specifies whether to enable file caching. Setting this parameter to on only takes effect when enable_aio_scheduler is set to on and obs_worker_pool_size is greater than or equal to 4.
Type: USERSET
Value range: Boolean
Default value: off
enable_disk_cache_recovery
Parameter description: Specifies whether file caching can be restored when the cluster is restarted.
Type: USERSET
Value range: Boolean
Default value: off
disk_cache_block_size
Parameter description: Specifies the size of a single block cached in the file system, in KB.
Type: POSTMASTER
Value range: an integer ranging from 8 to 8 x 1024 x 1024 x 1024
Default value: 1MB
disk_cache_max_size
Parameter description: Specifies the total caching size of the file system, in KB.
Type: SIGHUP
Value range: an integer ranging from 1 GB to 1 PB
Default value: 1/3 of the EVS disk capacity
The EVS capacity is divided into two parts: 1/3 x 2 replicas are used to store local persistent data (such as column-store indexes, row-store tables, and local column-store tables), and the other 1/3 is reserved for cache.
disk_cache_max_open_fd
Parameter description: Specifies the maximum number of files that can be concurrently opened in the cache of the file system.
Type: POSTMASTER
Value range: an integer ranging from 0 to INT_MAX
Default value: 1000
disk_cache_a1out_min_ratio
Parameter description: Specifies the length ratio of the a1_out queue at its minimum in the LRU2Q algorithm cached in the file system (the actual minimum length of the queue is disk_cache_a1out_min_ratio x disk_cache_max_size).
Type: POSTMASTER
Value range: a double-precision floating-point number ranging from 0 to DOUBLE_MAX
Default value: 0.5
disk_cache_a1out_max_ratio
Parameter description: Specifies the length ratio of the a1_out queue at its maximum on the LRU2Q algorithm cached in the file system (the actual maximum length of the queue is disk_cache_a1out_max_ratio x disk_cache_max_size).
Type: POSTMASTER
Value range: a floating point number ranging from 0 to DOUBLE_MAX
Default value: 8
disk_cache_a1in_ratio
Parameter description: Specifies the length ratio of the a1_in queue of the LRU2Q algorithm cached in the file system.
Type: POSTMASTER
Value range: a floating point number ranging from 0 to 1
Default value: 0.25
disk_cache_base_paths
Parameter description: Specifies the path for storing cache files in file caching.
Type: POSTMASTER
Value range: a string
Default value: disk_cache
install_as_standby
Parameter description: Specifies whether the node is the standby one during startup.
Type: POSTMASTER
Value range: Boolean
on indicates setting the node as the standby one.
off indicates setting the node as the primary one.
Default value: off
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