Hi, > "-o discard" is supported, but can have some negative consequences on > performance on some SSDs or at least whether it adds worthwhile performance > is up for debate ....
The problem is, that TRIM can't be benchmarked in a traditional way - by running one run with TRIM and another one without and later comparing numbers. Sure, enabling TRIM causes your benchmarks to run a bit slower in the first place (as the TRIM commands need to be generated and interpreted by the SSD, which is not free) - however without TRIM the SSD won't have any clue what data is "dead" and what needs to be rescued until you overwrite it. On my SandForce SSD I had disabled TRIM (because those drives are known for the good recovery without TRIM), and for now the SSD is in the following state: dd oflag=sync if=/some_large_file_in_page_cache of=testfile bs=4M 567558236 bytes (568 MB) copied, 23.7798 s, 23.9 MB/s 233 SandForce_Internal 0x0000 000 000 000 Old_age Offline - 3968 241 Lifetime_Writes_GiB 0x0032 000 000 000 Old_age Always - 1280 So that drive is writing at 24mb/s and has a write amplification of 3.1 - usually you see values between one and two. Completly "normal" desktop useage. - Clemens -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
