Taking care of mac SSD (minimizing writes/reads)

Discussion in 'MacBook Pro' started by Populus, Jul 9, 2017.

  1. Populus macrumors 6502a


    Aug 24, 2012
    Valencia, Spain.

    As some of you already know, I recently purchased my first retina MacBook Pro, and thus, I want to extend its lifetime as much as I can. I've been lucky, I have a Samsung SSD with 700MB/s write and 1300MB/s read, on my 2015 rMBP. Now, I want to preserve those speeds and its health.

    Due to the fact that it is a 128GB SSD, I want to take care of it; also, I'll need some extra storage in order to make room in my computer, that's why I'm going to purchase a JetDrive Lite 330 from Transcend. I'm sure you know this type of SD cards.

    But, the thing is, I'm making some test with an external USB 3.0 hard drive, and when I download anything to this Hard Drive, the Disk tab on Activity Monitor shows disk activity. I mean, if I download or copy any file to an external Hard Drive from an external source (internet, LAN, other USB drives...), that will count as writes on my internal SSD? I mean, even if I direct all my downloads to my SD card, even then, will degrade my SSD?

    It is important for me to know this, because if many GB of downloaded content, written in external drives, will degrade equally my SSD, there is no point in directing all my downloads and cache files to an external drive, in order to preserve the integrity of the system disk.

    Anyone knows the way Mac handles the data when downloading and copying to an external drive, or even moving files between two external sources (USB disk to USB disk, for instance)? Will that count against the lifespan of my System SSD? (I already know it is a lot of data needed over the years, but still)
  2. New_Mac_Smell macrumors 68000


    Oct 17, 2016
    Just make sure you enable TRIM support if it's an aftermarket SSD, google how to do this, pretty simple terminal command.

    Other than that just use it. You'll be waiting a fair few years for it to degrade. Not sure where this worry has come from but it should last a lifetime with a minimum of TRIM support. Worst case 2-4 years assuming you're writing 100% of the capacity every single day. But in reality you on average write maybe 10-15%, which gives a good 20 years of life.

    Honestly don't worry, there's no need to have any kind of OCD about SSD write cycles. They're far more resilient than HDDs after all.
  3. Populus thread starter macrumors 6502a


    Aug 24, 2012
    Valencia, Spain.
    It is the MacBook Pro Apple SSD, it is the original disk and have TRIM support by default.

    And I know you need tons of data written/erased over the years in order to degrade it. I know it, but I just want to minimize it, because this Mac has to be my main computer in the next 7-8 years, and I don't know if Apple replaces the SSD, I don't know if this SSD has MLC or TLC NAND cells, and so on...

    So, in order to prevent all the problems, I'd like to know if any download made directly to an external drive, or moving data between two drives connected to this Mac, count as writes and, thus, degrade the system SSD. That's all.

    To put things from another perspective, and not being called OCD: I just want to understand the Disk Activity tab from Activity Monitor... are all this written data (by the process called desktopservicehelper) being written both on my system SSD and after, into the external USB drive or SD card? Or they are written just once directly from the system RAM?

    Thank you.
  4. New_Mac_Smell macrumors 68000


    Oct 17, 2016
    If you write data to drive B it's writing it to B, A to A. System will cache on drive A and be continuously writing a little to it. It's as simple as that. It doesn't pass through the internal drive to get to the external, however the internal drive is running the OS so it's going to incur a small amount of r/w all the time.

    I'm sure they have it by default but I'd still run terminal to make sure that the software has it enabled, as TRIM makes a significant different. It isn't worth assuming it's on for the sake of a few minutes work.
  5. treekram, Jul 9, 2017
    Last edited: Jul 9, 2017

    treekram macrumors 65816

    Nov 9, 2015
    Honolulu HI
    If you copy a file using whatever Apple app (Finder, etc.) or the command line, it won't write to any other disk other the the disk(s) you copy to/from. Typically an application will download directly to the download location specified but I won't say always because who know's what applications do.

    Activity Monitor will report activity on all disks.

    If you want to see what is happening, open the Terminal app. Type in "diskutil list" and make a note as which disks are which (disk0, disk1, etc.). Then, before you do whatever activity you want to monitor (before a download, say), type in: iostat -d -w 1
    where 1 is the update time (in seconds). You can get out of the loop by pressing Ctrl-C. This will give you statistics on which disk is working. Your system disk is in use all the time (not every millisecond, but it will write/read stuff even when you're not doing anything on the computer).

    My default download directory is on a HDD because of what you're concerned about. A good majority of the downloads I do will never be used from my SSD so I download to an HDD. But for the good majority of users, their disk usage pattern is such that they won't use up the SSD write quota before they move on their next computer. However, the smaller the SSD, the smaller the lifetime write figure.

    (Update: Re the last paragraph, I should have mentioned that my main computer is a desktop computer so having an either internal or always connected HDD is no big deal. I have a mid-2012 MBP, but I usually don't surf the web on it.)
  6. ZapNZs macrumors 68020


    Jan 23, 2017
    Does your laptop have the SM951? If so, I believe this is a MLC drive.

    Even at 20 TBs my Samsung SSDs still are not even registering wear :p
  7. IllIllIll macrumors 6502a

    Oct 2, 2011
    OP sounds just like the guy who doesn't want to use his brakes on his car in order to minimize wear on the brake pads.
  8. Samuelsan2001 macrumors 604

    Oct 24, 2013
    Modern SSD's have been tested to death and will outlast your computer by years, they can all write petabytes of data before even beginning to fail so unless you are writing Terabytes of data a day to it's not even a consideration . Just use your computer and stop sweating the small stuff it will ruin your enjoyment of a wonderful tool but it is just that a tool to be used.

    This is from 2013 and they have only got better since then.

  9. throAU macrumors 601


    Feb 13, 2012
    Perth, Western Australia
    don't bother

    modern SSDs can read and write more data per day than you can possibly generate by normal use and still last for several years.

    look up storagereview ssd torture test (edit actually, the tech report link above) they did many petabytes on drives from a few years ago. basically many many total drive rewrites per day.

    basically several months of continuous synthetic continual max throughout torture. way, way in excess of any possible load you'd ever put on it via even hard core professional severe workload over several years. you simply wouldn't be able to generate or retrieve data via external sources fast enough in the real world to get anywhere close to the torture they put drives through.
  10. Fishrrman macrumors G5


    Feb 20, 2009
    Not worth worrying about.
    You'll wear out the rest of the laptop before the drive.
    Just use it.

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