DISK_STORAGE
Returns the amount of disk storage used by the database on each node. Each node can have one or more storage locations, and the locations can be on different disks with separate properties, such as free space, used space, and block size. The information in this system table is useful in determining where data files reside.
All returned values for this system table are in the context of the file system of the host operating system, and are not specific to Vertica-specific space.
The storage usage annotation called CATALOG indicates that the location is used to store the catalog. Each CATALOG location is specified only when creating a new database. You cannot add a CATALOG location annotation using CREATE LOCATION, nor remove an existing CATALOG annotation.
Storage Location Performance
The performance of a storage location is measured with two values:
- Throughput in MB/sec
- Latency in seeks/sec
These two values are converted to a single number (Speed) with the following formula:
ReadTime (time to read 1MB) = 1 / throughput + 1 / latency
- 1/throughput is the time taken to read 1MB of data
- 1/latency is the time taken to seek to the data.
- ReadTime is the time taken to read 1MB of data.
A disk is faster than another disk if its ReadTime is less.
Column Name | Data Type | Description |
---|---|---|
NODE_NAME |
VARCHAR |
The node name for which information is listed. |
STORAGE_PATH |
VARCHAR |
The path where the storage location is mounted. |
STORAGE_USAGE |
VARCHAR |
The type of information stored in the location:
|
RANK |
INTEGER |
The rank assigned to the storage location based on its performance. Ranks are used to create a storage locations on which projections, columns, and partitions are stored on different disks based on predicted or measured access patterns. See Managing Storage Locations in the Administrator's Guide. |
THROUGHPUT |
INTEGER |
The measure of a storage location's performance in MB/sec. 1/throughput is the time taken to read 1MB of data. |
LATENCY |
INTEGER |
The measure of a storage location's performance in seeks/sec. 1/latency is the time taken to seek to the data. |
STORAGE_STATUS |
VARCHAR |
The status of the storage location: active or retired. |
DISK_BLOCK_SIZE_BYTES |
INTEGER |
The block size of the disk in bytes. |
DISK_SPACE_USED_BLOCKS |
INTEGER |
The number of disk blocks in use. |
DISK_SPACE_USED_MB |
INTEGER |
The number of megabytes of disk storage in use. |
DISK_SPACE_FREE_BLOCKS |
INTEGER |
The number of free disk blocks available. |
DISK_SPACE_FREE_MB |
INTEGER |
The number of megabytes of free storage available. |
DISK_SPACE_FREE_PERCENT |
VARCHAR |
The percentage of free disk space remaining. |