Bill KING <[EMAIL PROTECTED]> wrote: > Okay, i've got PRAGMA synchronous = OFF and PRAGMA temp_store = memory > but i'm still seeing the system locking up and waiting for write when > writing to sd-cards
PRAGMA synchronous=OFF prevents SQLite from calling fsync() and fdatasync(). On most filesystems, that means all write() requests are queued by the OS and the data is not actually written out to the device until some time after the write() call returns - sometimes much later. But on some filesystems, calls to write() are synchronous. That is to say, write() does not return until the information has reached hard media. On Linux, whether or not a write() is synchronous is controled (in at least one way) by the "sync" option to the mount command when the filesystem is mounted. It is not uncommon for write() to be synchronous on removable media. I know that on my SuSE Linux laptop (on which I am typing this message) if I plug in a USB thumb drive, it automounts synchronous and write performance is abysmal. I have to go root, unmount the thumb drive, then remount it for asynchronous writes. Then it is blazing fast. You just have to be careful to unmount it before pulling it out of the USB slot.... -- D. Richard Hipp <[EMAIL PROTECTED]> ----------------------------------------------------------------------------- To unsubscribe, send email to [EMAIL PROTECTED] -----------------------------------------------------------------------------
