How much storage should you leave unused on a Mac’s SSD?
If you look at how much storage space there is to keep the SSD unused, you’ve probably got recommendations between 0 and 50 percent, and you may be disappointed with how to sort the exact number. When you have a 1TB or 2TB drive, keeping even 20 percent (200GB or 400GB) unused can seem unnecessary and expensive.
For most consumer uses and even for many professionals, you can mistake the bottom of empty storage, even filling a drive up to what you think is 100 percent full, depending on how you use the SSD now and plan for the future. After reading this column you may decide not to worry about free space at all or choose to leave about 30 percent of your SSD empty.
Let’s start with the bloody details. (If you want to avoid these and avoid giving advice, go to the section below.)
Why an SSD requires free space
SSDs are quiet, low-power, long-lasting, and resilient, but they will ultimately fail, just like a hard disk drive (HDD), albeit in a very different fashion. This analysis of storage and backup firm backblaze from 2019 is a thorough, not too technical, look at the differences between the two types of storage.
An HDD has a lot of internal running and spinning parts when an SSD is in a “solid state” and everything happens as a result of electrical operation in the drive chip. More specifically, very little voltage is used to read data from an SSD memory cell and there is no actual wear; Writing data requires a higher voltage which eventually wears out the storage bits.
Approximately a limited number of times on an SSD, each cell can be written with the overall expected total input in its lifetime drive. On an HDD, since the writing of data involves magnetic changes, the same level of wear will not occur to update files to the same location on the disk. (You can use a utility like DriveDx to provide a running estimate of the remaining lifetime on an SSD or HDD. It has some Apple-related limitations when it comes to monitoring external drives.)
SSD firmware works to rotate through memory cells, each unit that saves 1 to 4 bits and equalizes wear throughout the entire drive. Otherwise, a frequently used cell will burn out much earlier than other cells. Every time you save a document, copy files, or otherwise write data to an SSD, or whenever the operating system takes an automatic step of the same kind, the cells that the SSD writes are completely different from the previous data. Was saved. SSD firmware tracks all of these — it’s operating system and non-stop for you.
This is compounded by the fact that SSDs divide memory cells into larger units known as PagesAnd the pages are grouped 7 Block. Depending on the SSD’s chips design, a page can hold 2K to 16K and a block can be between 256K and 4MB. Because of how free storage is distributed, whenever an SSD writes data, it may be able to write the value of only one page, or it may write a whole block – so one bit of data conversion can mean writing up to 4MB.
Overview: Space to extend the life of an SSD
Some of the cells that combined with that overhead failed, leading to early manufacturers Additional arrangements Storage by creating extra capacity you (and the operating system) never see. This invisible part saves an SSD its entire lifetime, allowing it to write smaller pages more frequently than large blocks. An article by drive maker Seagate compared it to a 15-square game.
This extracurricular storage is hidden in drive marketing by exploiting the difference between the power of the two and the power of 10. A “500GB” drive offers 500 billion bytes of storage. However, memory chips are marked at 2 power. The closest value to one billion is one “gibibyte” or GiB, 1024 (2 ^ 10): 1 GiB is 1,073,741,824 bytes. A 500GiB drive has 537GB of storage, but you can only see 500GB, which is an extra 37GB. Instinctive The amount of extra provision made for the drive.
For most consumers, even when an SSD is your startup volume, you can use 100 percent of the SSD’s storage as shown in Finder and still enjoy a long and happy life from your drive.
SSDs have an estimated lifespan of about 5 to 10 years, based on a number called Terabyte Writing (TBW), which reflects how a drive will work with well-distributed writing activities through a certain amount of data. Along with Samsung’s affordable T7 External Drive series, the 1TB model has a 360TBW value, which equates to an average of 200GB of data written per day for 5 years. High-powered TBWs tend to have higher numbers because they are expected to gain more writing experience than their size.
Samsung Data Center also offers a concise and understandable white paper on additional provisioning aimed at users, but it also has an incredibly useful three-line chart that lets you decode the utility of having more unused storage on a drive. These factors are important in data centers where SSDs gain much more writing experience than personal computers.
Lifetime factor is shown as 1, with no additional provision, some only available on data-center-based drives, without any hidden SSD stash.
Move up to 6.7 percent, the amount that Samsung and other SSD manufacturers bake in their consumer drives and the Lifetime Factor more than doubled to 2.09. Baseline used for Samsung’s TBW statistics for consumer-level SSDs.
Save a total of 28 percent, and the factor goes to 5.22. It can take a drive that can last up to 5 years and it can extend up to about 12 years. But perhaps you want an overhead on an SSD that you use to write files more intensively than the average user, such as those used for daily live recording or audio and video editing.
How much storage should you keep as empty? Let’s look at that.
How much overprojection
Apple, Samsung, and other consumer SSDs have a quick list of recommendations for additional measures, with 7% or more excluded:
5 to 20 percent for a Mac startup volume or external drive, depending on usage intensity
A higher percentage can be guaranteed for the M1-Series Mac
Around 0 percent for external drives that are used to offload most of the data that is read later but rarely rewritten
A Mac’s startup volume will experience much more writing activity than most external drives. You can always choose to leave a significant fraction of your startup volume between 5 and 20 percent above the amount inherent in the drive. I would recommend a lower range for general use and if you use software that constantly writes and transfers files to the drive.
However, it is always a good idea to keep some storage free for a macOS startup volume. Apple will fill in the blanks in the main volume partition as required for temporary machine files, “swap” files (used when there is memory pressure to write data to the drive) and time machine snapshots before transferring to time machine volume.
Unused storage on an SSD is considered as free space: for the purpose of writing data, storage that the operating system did not allocate calculations for additional arrangements.
The M1-Series Mac has an extra bit of concern to keep the built-in SSD happy as long as possible. Apple has engineered M1-series chips so that a Mac cannot boot if its internal SSD fails, as it saves the provisioning information needed to get started from an external drive. If your internal SSD fails prematurely, you will not be able to switch to an external SSD like Intel Mac. That factor in your use.
On an external SSD that is not used to launch your Mac, you should decide based on the intensity of its use. If you’re offloading data to an SSD or using it as a time machine volume, increasingly adding data and overwriting only when needed, you can move closer to full use without worrying about shortening the lifespan. With the drive used to read most of the data, it will experience very little wear.
However, if your external drive is constantly bumping into read and write – especially for large files deleted, modified or moved – save a margin, even a significant one, unless you want to use all its space and budget a quick replacement Cycle.
This Mac 911 article answers a question posed by MacWorld reader Donald.
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