What Are L1 and L2 Cache? Disk Caching Explained

When you set up a disk cache, you often see references to L1 cache and L2 cache. The names come from a simple idea: put the fastest, smallest storage closest to the action and lower the data into slower storage as you go outward. Your CPU already works this way with its own L1, L2, and L3 caches. A disk cache applies the same layered approach to your drives.

In a disk cache, L1 is the RAM cache and L2 is the SSD cache. This guide explains what each tier does, how they work together, and how to configure both in Qiling Fast Cache for the best performance in Windows 11.

PAGE CONTENT

• Why Caches Have Levels
• L1 Cache: The RAM Tier
• L2 Cache: The SSD Tier
• L1 vs L2 Compared
• How L1 and L2 Work Together
• Configure the L1 RAM Cache
• Configure the L2 SSD Cache
• Set Up the Cache Task in Qiling Fast Cache
• FAQs About Cache Levels
• Back Up Windows Before You Change Settings

Why Caches Have Levels

Faster storage is always smaller and more expensive than slower storage. RAM is extremely fast but limited in size; an SSD is slower but much larger; an HDD is the slowest and the largest. No single tier can be both vast and instant, so a cache system stacks them.

The rule is simple: keep the most frequently used data in the fastest tier, the next most used data in the second tier, and everything else on the original drive. Data is promoted toward the fast tiers as it proves popular and demoted when it stops being used.

A cache tool needs two things to do this well — a very fast tier for the hottest data and a large tier to hold a broad working set. That is exactly what L1 and L2 provide.

L1 Cache: The RAM Tier

The L1 cache uses part of your system memory. Because RAM is the fastest storage in your PC short of the CPU caches themselves, L1 delivers the lowest possible latency.

Key traits of the L1 RAM cache:

• Fastest access — reads are served in microseconds.
• Limited size — bounded by how much RAM you can spare, usually a few gigabytes.
• Volatile — cleared on shutdown or reboot, so it must refill each session.
• Holds the hottest data — the blocks you access most often.

L1 is ideal for the small set of files that Windows, your browser, and your daily apps touch constantly.

L2 Cache: The SSD Tier

The L2 cache uses a fast SSD or NVMe drive. It is slower than RAM but far larger and, crucially, it is persistent — the data stays cached across reboots.

Key traits of the L2 SSD cache:

• Large capacity — can hold tens or hundreds of gigabytes of hot data.
• Persistent — survives restarts, so it stays warm and keeps a high hit rate.
• Faster than the source drive — even a modest SSD outpaces an HDD by a wide margin.
• Broad coverage — catches the working set that does not fit in RAM.

L2 is what makes a cache genuinely useful day after day, because it does not reset when you turn off the PC.

L1 vs L2 Compared

	L1 Cache (RAM)	L2 Cache (SSD)
Medium	System memory	SSD or NVMe
Speed	Fastest	Fast
Size	Small (a few GB)	Large (tens to hundreds of GB)
Persistence	Volatile	Persistent
Best for	Hottest, most-read blocks	Broad working set
Cost	Uses spare RAM	Needs a spare SSD

Used individually each tier helps. Used together they cover both the ultra-fast repeats and the larger working set.

How L1 and L2 Work Together

In a two-tier cache, the flow for each read is:

• Check L1 (RAM) first. A hit here is the fastest possible result.
• If L1 misses, check L2 (SSD). A hit here is still much faster than the original drive.
• If both miss, read from the source drive and promote the data into L2, and into L1 if it is used often enough.

Over time the hottest data rises to L1, the rest of the working set settles in L2, and the slow drive is touched only for genuinely new or rarely used data. This layered design is why a two-tier cache outperforms a single-tier one: it captures both the extreme frequency of a few blocks and the broader spread of many blocks.

Configure the L1 RAM Cache

The RAM tier is set when you create a cache task, and it is a decision separate from choosing which drive to accelerate. Configure it deliberately rather than accepting whatever the dialog suggests.

Step 1. In the cache task dialog, set the cache medium to RAM, so Qiling Fast Cache uses system memory as the fastest tier.

Step 2. Set the L1 size from your free memory, not your total memory. About one-third of what is genuinely available at a typical workload is a reasonable starting point.

Step 3. Leave the rest for Windows and your applications — at least 8 GB — and check Task Manager after a day of normal use. If committed memory climbs close to the physical limit, reduce the L1 size.

Key points to remember:

• Fastest tier. Reads served from L1 have the lowest latency in the system.
• Holds only the hottest blocks. A larger L1 does not help once it covers your hottest data; it only takes memory away from applications.
• Volatile. L1 empties at every shutdown and must warm up again each session. The L2 tier is what keeps the cache warm; see What Is Cache Warm-Up?

Example: a 16 GB PC with about 9 GB free at a typical workload can assign roughly 3 GB to L1. On a machine that is already close to full, keep L1 at 2-4 GB or rely on the SSD tier alone.

Configure the L2 SSD Cache

The SSD tier is configured in the same dialog, and it is the tier that keeps the cache useful day after day.

Step 1. Choose an SSD or NVMe partition as the L2 medium. Prefer a drive other than the one being accelerated, so the cache and the source drive do not compete for the same device.

Step 2. Set a generous size. For a system drive, 64-128 GB is a good starting range; for large game, media, or project libraries, scale it to match the working set you actually reuse.

Step 3. Keep 10-20 percent of the SSD free. The cache can never be larger than the partition's available space, or larger than the drive it accelerates.

Step 4. Accept the endurance trade-off knowingly: caching adds writes to the SSD. On a modern drive with a sensible endurance rating the extra wear is modest; see How to Extend Your SSD Lifespan if the drive is small or old.

Key points to remember:

• Persistent. L2 survives reboots, so it stays warm and holds its hit rate.
• Much larger than L1. L2 carries the broad working set while L1 keeps only the hottest slice of it.
• Faster than the source drive. Even a modest SATA SSD outpaces an HDD by a wide margin.

Set Up the Cache Task in Qiling Fast Cache

With both tiers decided, creating the task is a short procedure.

Step 1. Download and install Qiling Fast Cache.

• Free Download
• Windows 11/10/8/7, 100% Secure

Step 2. Open the app and click the + button to create a new cache task.

Step 3. Apply the L1 and L2 settings from the two sections above, then select the drive to accelerate — usually the HDD you want to speed up — and click OK.

Step 4. Watch the hit rate. The main window shows how much is served from the cache. See How to Check Cache Hit Rate for details.

FAQs About Cache Levels

Are L1 and L2 the same as CPU caches?

No. CPU L1/L2/L3 caches are tiny and built into the processor. Disk cache L1/L2 borrow the same layered idea but work on your drives, using RAM and SSD.

Do I need both tiers?

No. A single-tier cache works, but combining a small RAM tier with a large SSD tier gives the best balance of speed and capacity.

Which tier should be larger?

L2 should usually be much larger than L1. RAM is valuable and limited, so keep L1 modest and let the SSD tier hold the bulk of the working set.

Why does the L1 hit rate reset after a reboot?

RAM is volatile, so the L1 cache starts empty each session and refills as you work. The L2 SSD cache persists and stays warm.

How much RAM should the L1 cache use?

Base the size on your free memory rather than the total, and keep at least 8 GB for Windows and your apps. On a 16 GB system with roughly 9 GB free, about 3 GB is a sensible starting point.

Back Up Windows Before You Change Settings

Configuring a cache is safe, but if you also change storage settings, a backup protects your system. Qiling Disk Master creates a full Windows image you can restore from if anything goes wrong.

• Free Download
• Windows 11/10/8/7, 100% Secure

Part 1: Create a Full System Backup

Step 1. Install and open Qiling Disk Master. On the home screen, open "Backup and Recovery" and choose "System Backup". This option automatically includes Windows and the hidden boot partitions, so you do not have to select them one by one.

Step 2. Check the source. The disk where Windows is installed and its system partitions are already ticked for you. If you only need your personal documents, run a separate "File Backup" task instead.

Step 3. Click the destination box and choose where the image should be saved. Use an external HDD or SSD, a NAS, or any drive other than the one Windows is installed on, and make sure it has enough free space.

Step 4. Review the task summary and click "Proceed". Wait until the progress bar reaches 100%. Do not unplug the drive or turn off the PC while the backup is running.

Part 2: Restore Windows from the Backup

Step 1. Open Qiling Disk Master again, go to "Backup and Recovery", and select the recovery option. Your backup images are listed, so pick the one you created before the changes began.

Step 2. Choose the target disk or partition. Normally you restore to the original system disk. If the drive was replaced, select the new disk instead, and the restore rebuilds Windows together with its boot partitions.

Step 3. Preview the restore plan, click "Proceed", and confirm the warning. The PC restarts to finish the job, and Windows comes back exactly as it was on the day the image was created, with your files and programs intact.

Conclusion

L1 and L2 are the two tiers of a disk cache. L1 is the RAM cache — the fastest tier, holding the hottest data but limited in size and cleared on reboot. L2 is the SSD cache — larger and persistent, holding the broader working set across restarts. Used together, they capture both the extreme frequency of a few blocks and the wider spread of many, which is why two tiers beat one. Qiling Fast Cache supports both levels: a modest RAM tier for the hottest reads and a generous SSD tier for everything else, all accelerating your slowest drive.

Protect your PC with Qiling Backup—create a system image before your next round of settings changes.

For more Windows 11 performance guides, see Windows 11 Fast Cache, Write Caching vs Read Caching, How to Check Cache Hit Rate, SSD Cache vs RAM Disk, and Best SSD Cache Software for Windows 11.

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