Hello. I've found this old thread http://thread.gmane.org/gmane.comp.file-systems.ext4/16386/focus=16444 and wanted to contribute a piece of my exiriance. As I don't know if putting right subject will be enough to make reply on right thread, I'm putting to BCC addresses of all coresponders in old thread. I've noticed that there is a difference between /sys/fs/ext4/sdXX/lifetime_write_kbytes and host writes read from SSD itself. I'll put aside issue of losing lifetime_write_kbytes accuracy after unclean reboot/shutdown: http://thread.gmane.org/gmane.comp.file-systems.ext4/19734 Guess that session_write_kbytes doesn't succed to be added to lifetime_write_kbytes in that particular case. In normal desktop operation "host writes" counter on SSD increases at roughly ~2/3 compared to lifetime_write_kbytes. My best guess is that host itself uses a lot of optimisation to reduce writing to NAND itself. Besides that, I've noticed that my commit=100 mount option helps also. Changing (just for testing) to something realy big, like commit=9000, gave even further improvement, but not worth staying with risk of losing (that much) data. It seems that ext4 writes a lot to filesystem, but many of those writes are overwrites. If we flush them to host just once in 100 seconds, we're getting a lot of saving. As I wanted to make even my swap TRIMable, I've put it in the file on ext4 instead of separate partition. I've made it using dd with seek=500 bs=1M options. ext4's lifetime_write_kbytes increased by 500MB, and host writes did not incrase at all, even after 100 seconds. Ok, I know that ext4 did not write 500MB of data to filesystem, but this is one more thing why one should not trust lifetime_write_kbytes. So, the moral of my story would be not to trust lifetime_write_kbytes, but to read host writes from SSD. I noticed that Intel's Solid State Drive Toolbox software (running in Windows) gives the amount of Host Lifetime Writes that equales to S.M.A.R.T attribute 225 (Load_Cycle_Count) multiplied with 32MB. That's the way I track it in Linux. Nebojsa Trpkovic -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
