SSD's, SD-Card, Compact Flash and most other solid state, writable storage has built in wear leveling. Why SSD's need the TRIM done is because when data is deleted it's only marked as deleted but isn't immediately marked as being available to be written over, unlike disk drives where a file marked deleted can immediately be written over and likely will be with the very next bunch of writes. That may make it much easier to recover deleted files from an SSD. Doing a TRIM is akin to writing zeroes to all the free space on a hard drive. TRIM an SSD and all space occupied by deleted files is marked as actually empty and available for immediate writing, as chosen by the wear leveling system. TRIM an SSD and your deleted data is very likely gone for good, especially if anything is written to it after the TRIM.
A well designed SSD shouldn't need TRIM done, it'll get around to re-using every block in its turn, eventually. If it does lag in performance after a lot of files have been written, deleted and written many times, then perks up after a TRIM, then it's not a well optimized design. While SSD's can withstand many petabytes worth of writes, which for the vast majority of users would be many years worth of use, their failure modes tend to be extremely sudden and often very destructive to data. Several of the brands of 'consumer grade' SSDs have an error counter with a hard limit (Intel) or some unspecified set of conditions - at which point the drive bricks itself and becomes unreadable. Your data is locked inside, unrecoverable without sending it off to a specialist. Intel's enterprise SSDs don't self-brick. When their error counter maxes out, they slow the write speed wayyyyy down as a prompt to make a backup *right now*. Intel has produced a line of "prosumer" SSD's mounted on PCIe cards, with the same recoverable fail mode as their enterprise models. I've had one hard drive fail that lost data I didn't want to lose. It was a Maxtor, IIRC single digit gigabytes, apparently it had a disk stored firmware failure. I've had one other that failed but didn't contain anything I cared about or didn't have somewhere else. It was a not very old 15 gig IBM "Deathstar". A second one, same model, that I bought new at the same time, would conk out if it got the least bit warm. If it had a fan blowing on it inside the PC, it was fine. Would always pass every test I threw at it, even when heated up. Install Windows, boot up and without cooling it'd start clicking and die partway through. I gave that one away, with the admonition to not put anything critical on it and to keep a fan blowing on it. Then there's the issue that SSD's have not proven to be stable long term without being periodically powered up. A spinning hard drive can be written full of data, pulled out, put on a shelf and all the data will be readable decades later. Don't be surprised if you put a computer with an SSD in the back of a closet somewhere, then pull it out next decade and it won't boot because the storage is corrupted or blank. I'll wait a bit longer for SSD to mature more before I'll rely on it for data I don't ever want to lose unless I delete it. On Saturday, October 28, 2017, 1:58:11 AM MDT, Chris Albertson <[email protected]> wrote: Forgot to say... It yu want to get maximum life from an SSD. Yo need to enable its built-in "TRIM" function. What this does is load balance the writing over the entirety of the SSD so all the sectors (pages) get written to. Older version of Linux don't do this automatically.. Yu would have to have a cron script run periodically. The file system on a hard drive tries too keep data near the outside edge of the drive as that is there the tangental velocity of a spinning disk is greatest and it also ties to keep the data in a compact area (de-fragmente) For an SSD you want exactly the opposite of this. Yu want to keep the data scattered randomly all over the drive. It will be faster and last longer if data is sparsely distributed. TRIM does this. ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
