Vector supports asynchronous gather I/O. This improves the speed of write operations such as loading, sorting, and spilling to disk.

At startup, the Vector Server tests to see if the operating system supports gather I/O (also known as vectored I/O). If the test fails, Vector disables using asynchronous gather I/O but still uses asynchronous I/O to interleave I/O with processing.

Setting the configuration parameter [cbm] gather_io_enabled (see gather_io_enabled) to false tells the Vector Server not to check for gather I/O support and to disable its use.

If Vector automatically disables the use of gather I/O, a warning message is written to vectorwise.log. If gather I/O is disabled, Vector will not achieve optimal write performance on fast I/O subsystems (for example, multiple SSDs organized in RAID-0). Performance should still be relatively good on slower hardware.