External SSD drives without Trim support

Discussion in 'iMac' started by dimme, Apr 9, 2019.

  1. dimme macrumors 68000

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    SF, CA
    #1
    I have a few external SSD drives is a USB3.1 and 3.0 cases. They are Samsung 850 & 860 EVO drives. I store my photo collection and working files on these and they are backed up. Do i need to be concerned because TRIM is not supported on these drives. What are the "side effects" of not having trim support.
     
  2. Weaselboy Moderator

    Weaselboy

    Staff Member

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    California
    #2
    No TRIM results in a little more wear on the drive, but these things last about forever anyway, so I would worry too much about it.

    No TRIM can also over time lead to slower write speeds, but again, lots of people use these drives without TRIM and don't see the slowdowns.

    So while TRIM is a good thing and should IMO be enabled when possible, not having it likely will not cause a problem. Even if it does and the drive slows some, it will still work.
     
  3. dimme thread starter macrumors 68000

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    SF, CA
    #3
    Thanks for the info. So there should be no concern about data loss? Would a good practice be to backup, reformate and restore yearly to combat the lack of trim?
     
  4. Weaselboy Moderator

    Weaselboy

    Staff Member

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    #4
    Lack of TRIM won't impact data loss issues and a reformat is not going to resolve the issue. I would just use the drive like any other and not sweat it.
     
  5. adamk77, Apr 9, 2019
    Last edited: Apr 9, 2019

    adamk77 macrumors 6502a

    adamk77

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    #5
    If you do a full reformat then it will have the opposite effect -- it'll shorten its lifespan.

    A SSD is made up of blocks. A block (Block 1 below) is made up of pages (A, B, C).

    Block 1
    +-------------------+
    | +---+ +---+ +---+ |
    | | A | | B | | C | |
    | +---+ +---+ +---+ |
    +-------------------+

    It can only write to it at the page level. Erasures can only happen at the block level. So if the SSD writes to A, B, C but then later deletes A, it would need to copy B and C to another block and then do an erase on the entire Block 1 to reclaim the freed space A. IOW, it can't just erase A without erasing the entire Block 1.

    This is what's called a Write Amplification (
    https://en.wikipedia.org/wiki/Write_amplification) because a single write command is amplified into multiple write operations. And this is what's happening inside a drive without TRIM.

    There's not much you can do to combat this save for only reading from the SSD. So I would just use it as it is and have a sensible backup plan to mitigate data loss. Something that you can do that will improve the performance of the SSD is to keep around 20-25% of the SSD free for it to efficiently do the delete operation as described above.
     
  6. IngerMan macrumors 65816

    IngerMan

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    Michigan
    #6
    Are you saying you should only use 20-25% of the SSD capacity or the opposite?

    Also are some fo the SSD manufactures using a type of Garbage collection to combat lack of Trim?
     
  7. adamk77, Apr 9, 2019
    Last edited: Apr 9, 2019

    adamk77 macrumors 6502a

    adamk77

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    #7
    Nice catch! Yes, I got it mistakenly reversed. Fixed.

    Garbage collection is already being done. It's is basically doing what I described in my earlier post but done in the background.

    With or without TRIM, the flash controller should still be doing wear leveling (https://en.wikipedia.org/wiki/Wear_leveling).
     
  8. talk2jorge, May 11, 2019
    Last edited: May 11, 2019

    talk2jorge Suspended

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    May 11, 2019
    #8
    Wow. So uninformed.

    Firstly, I'd like to say I am not here for flames or trolling. I used to have an account 6 years ago but I guess it was deleted after not using it for some time.

    Secondly. Wow. Just wow. Ok Is this SLC, MLC, TLC, QLC? Does this drive have cache? Is this a small drive or a large drive?

    https://forums.macrumors.com/thread...on-mac-os-sierra.2119738/page-2#post-27353473

    See my post here. Yes. It is supported. No Apple does not turn it on because UNMAP is not always supported by the drive enclosure. It's also up to the SSD to accept the commands as well.

    The drive will expire if you have DRAM-less. It will fail if there are fewer chips (120 will fail faster than 480 or 960). If you are doing video it will fail fast. If you are always using it it will fail fast. If you are keeping it 90% full then it will fail. Garbage collection is ONLY useful if you got the cache drive. Even then I am not 100% certain that that extra cache is utilized without drivers. Definitely not on Samsung drives. Let's say you installed it IN the Mac. The over provisioning and cache is only available with driver. None of that is available on Macs. Only Windows. It'll be fast for a good month or two but slowly begin to show signs of wear.

    Now for the USB 3.1 question: Here is what will happen. You'll put the drives in your enclosure. You'll use them. Next thing you know you'll be reading or writing to them and they will pause. Then the pauses will become more frequent. Then Mac will start spending extra cpu cycles on this drive because it has to keep searching for space to write and those pauses won't help. As I mentioned, I am not 100% sure the cache is effective. I am testing a 512 now. it shows up as 480 though.

    NOTE: There is a reputable retailer that only sells Mac stuff. They claim to have drives specifically designed for Macs. The cache kind. They are pricey. I have not tested them but again, that is only for internal. I don't know about USB. They also sell TB PCI enclosures with PCI cards and NVME drives. It's expensive. I am not here to sell for them so I am not mentioning their name.

    Ok off to see Endgame.
     
  9. cynics macrumors G4

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    Jan 8, 2012
    #9
    SSD Controllers (which is an SoC, processor, sdram (cache memory), its programming) and their associated cache work independently of the OS. The OS doesn't know what is written at a block level and the SSD doesn't know what is written at a file system level.

    Only time the SSD controller get a bit more insight from the OS is when it sends the TRIM command data to make its garbage collection a more efficient.

    Matter of fact the SSD controller is so independent of the OS that there is a capacitor(s) on in it so if power is lost or its removed from the computer while operating it has time to move the data off its SDRAM and onto NAND. Literally writing data while not connected to a computer albeit momentarily.

    Newer controllers have a way to "refresh" the drive specifically for TRIM-less environments.

    This is from a full (20gb remaining) 1tb Adata thats been in my PS4 Pro for about 2 years (upgraded it to 2tb).

    Screen Shot 2019-05-11 at 9.25.14 PM.png
     
  10. Fishrrman, May 12, 2019
    Last edited: May 13, 2019

    Fishrrman macrumors P6

    Fishrrman

    Joined:
    Feb 20, 2009
    #10
    All I can do is report on my own experiences, over the course of several years.

    I've never had a "TRIM" problem with any SSD I've used, for booting or otherwise.
    That includes drives mounted via USB3, USB2, firewire.
    Boot drives, data drives, no difference.

    TRIM is a molehill that some folks transformed into a mountain.
    It might affect you, but the chances are few. For most folks, I reckon it will never come into distant view.
     
  11. mikehalloran macrumors 65816

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    Oct 14, 2018
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    The Sillie Con Valley
    #11
    There is so much that you don’t know about this. Yikes! This whole post should be ignored.
     

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10 April 9, 2019