The Linux SCSI programming HOWTO: Driver Defaults

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## 13. Driver Defaults

## 13.1 Transfer Lengths

Currently (at least up to kernel version 1.1.68) input and output sizes have to be less than or equal than 4096 bytes unless the kernel has been compiled with `SG_BIG_BUFF` defined, if which case it is limited to `SG_BIG_BUFF` (e.g. 32768) bytes. These sizes include the generic header as well as the command block on input. `SG_BIG_BUFF` can be safely increased upto (131072 - 512). To take advantage of this, a new kernel has to be compiled and booted, of course.

## 13.2 Timeout And Retry Values

The default timeout value is set to one minute (`Timeout` = 6000). It can be changed through an ioctl call (see section sec-ioctl ). The default number of retries is one.

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