A scratch disk is the temporary workspace creative apps use for caches, previews, and overflow when RAM runs out. On a desktop you might dedicate a whole drive to it. On a creator laptop the question is trickier, because you usually have limited internal bays. Here is when a dedicated scratch disk actually helps and how to set one up without buying a second machine.
What a scratch disk does
Apps like Photoshop, Premiere Pro, After Effects, and Lightroom write render caches, media caches, and virtual-memory overflow to a scratch location. When that location is slow, or shares a drive that is busy reading your source footage, you get sluggish scrubbing, laggy previews, and stalls during export. A fast, separate scratch disk lets the app read source media from one drive while writing cache to another, removing the bottleneck.
Scratch disk options for laptops
| Option | Speed | Best for |
|---|---|---|
| Second internal NVMe | Excellent | Serious editing, if you have a spare M.2 slot |
| External USB4/TB SSD | Very good | Portable scratch, most flexible |
| External USB 3.2 SSD | Good | Budget scratch, still beats one busy drive |
| Same system SSD | Fine if fast + roomy | Light editing, single-drive laptops |
| Any spinning HDD | Poor | Avoid for scratch |
Do you actually need one?
Light editing on a fast, roomy SSD: no
If you shoot 1080p or light 4K, run 16–32 GB of RAM, and your single NVMe has plenty of free space (keep at least 15–20 percent free for the SSD to breathe), the default scratch on the system drive is fine. A modern PCIe 4.0 drive is fast enough that a separate scratch adds little.
Heavy 4K/multicam, big comps, or a full SSD: yes
Once you edit high-bitrate 4K, run multicam, stack effects in After Effects, or your system drive is nearly full, a dedicated scratch disk pays off. Separating source reads from cache writes smooths playback and shortens exports, and it keeps your fast-filling caches off the OS drive.
Setting one up on a laptop
The cleanest option is a second internal NVMe if your laptop has a free M.2 slot—point each app’s cache/scratch preference at it. If not, an external SSD over USB4 or Thunderbolt delivers near-internal speeds and travels with you; a USB 3.2 Gen 2 drive at around 1000 MB/s is a solid budget alternative that still beats hammering one busy drive. In each app’s preferences, set the media/render cache and scratch location to the dedicated drive, keep it under about 70–80 percent full, and clear old caches periodically so it does not silently fill up.
Organising a fast three-drive-style workflow
Even on a two-slot laptop you can approximate the classic editor’s multi-drive layout that keeps everything responsive. Treat your system NVMe as the OS-and-apps drive, use the second internal (or a fast external) as a combined project-and-cache drive, and keep bulky finished exports and archives on a roomier external you are not editing from. The principle is simply to avoid asking one drive to read source footage, write cache, and hold the export all at once during a demanding timeline. A related tip: for scratch and cache, drive endurance is worth a thought because these locations see heavy sustained writes—a mainstream TLC NVMe with a healthy terabytes-written rating handles years of this comfortably, whereas the cheapest QLC drives can slow down once their cache fills during a long render. You do not need exotic hardware, just a deliberate split so no single disk becomes the session’s bottleneck. Set it up once and every scrub, preview, and export feels quicker.
FAQ
Is an external SSD fast enough for a scratch disk?
Over USB4 or Thunderbolt, yes—those reach multi-gigabyte-per-second speeds close to internal NVMe. Even a USB 3.2 SSD around 1000 MB/s works well as scratch because the win comes from separating cache writes from source reads, not just raw speed.
Can I just add more RAM instead of a scratch disk?
More RAM reduces how often apps spill to the scratch disk, so it helps—but caches and previews still get written regardless of RAM. For heavy 4K work you generally want both adequate RAM and a fast scratch location; they solve different bottlenecks.
Bottom line
You need a dedicated scratch disk on a creator laptop when you edit heavy 4K, run big compositions, or your system drive is filling up—otherwise a fast, roomy NVMe handles it fine. When you do need one, a second internal NVMe or an external USB4/Thunderbolt SSD gives near-internal speed, keeps caches off the OS drive, and noticeably smooths playback and exports.
