11.9. Using preallocation for data volumes
The Containerized Data Importer (CDI) can preallocate disk space to improve write performance when creating data volumes. You can enable preallocation for specific data volumes.
11.9.1. About preallocation
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The Containerized Data Importer (CDI) can use the QEMU preallocate mode for data volumes to improve write performance. You can use preallocation mode for importing and uploading operations and when creating blank data volumes.
If preallocation is enabled, CDI uses the better preallocation method depending on the underlying file system and device type:
fallocate-
If the file system supports it, CDI uses the operating system’s
fallocatecall to preallocate space by using theposix_fallocatefunction, which allocates blocks and marks them as uninitialized. full-
If
fallocatemode cannot be used,fullmode allocates space for the image by writing data to the underlying storage. Depending on the storage location, all the empty allocated space might be zeroed.
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