On Thu, 2013-09-12 at 16:18 +0200, Julian Andres Klode wrote: > Hi, > > I installed my new laptop on Saturday and setup an ext4 filesystem > on my / and /home partitions. Without me doing much file transfers, > I noticed today: > > jak@jak-x230:~$ cat /sys/fs/ext4/sdb3/lifetime_write_kbytes > 342614039 > > This is on a 100GB partition. I used fstrim multiple times. I analysed > the increase over some time today and issued an fstrim in between: <snip> > So it seems that ext4 counts the trims as writes? I don't know how I could > get 300GB of writes on a 100GB partition -- of which only 8 GB are occupied > -- otherwise. The way fstrim works is that it allocates a temporary file that fills almost the entire free space on the partition. I believe it does this with fallocate in order to ensure that space for the file is actually reserved on disc (but it does not get written to!). It then looks up where on disc the file's reserved space is, and sends a trim command to the drive to free that space. Afterwards, it deletes the temporary file. So what you are seeing means means that it's probably just an issue with the write accounting, where the blocks reserved by the fallocate are counted as writes. > My smart values for my SSD are: > > SMART Attributes Data Structure revision number: 1 > Vendor Specific SMART Attributes with Thresholds: > ID# ATTRIBUTE_NAME FLAG VALUE WORST THRESH TYPE UPDATED WHEN_FAILED RAW_VALUE > 241 Total_LBAs_Written 0x0003 100 100 000 Pre-fail Always - 1494 You should be able to confirm this by checking the 'Total_LBAs_Written' attribute before and after doing the fstrim; it should either not go up, or go up only be a small amount. Although to be honest, I'm not sure what this is counting - if that raw value is actually LBAs, that would only account for 747KiB of writes! I guess it's probably a count of erase blocks or something - what model is the SSD? -- Calvin Walton <calvin.walton@xxxxxxxxxx> -- 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
