dasd on Mac: the background task scheduler, why it wakes your Mac, and when it is stuck

What dasd does

dasd runs the Duet Activity Scheduler, the part of macOS that answers the question "is now a good time?" for background work. Instead of each app running its own timer, apps and system services submit activities with constraints: run once a day, only on power, only when the user is idle, only on Wi-Fi, needs the disk, can be delayed up to six hours. dasd holds all of them and, using the usage model from coreduetd and the power state from powerd, picks the moment to launch each one.

The scale is larger than most people expect. Howard Oakley of The Eclectic Light Company traced it in 2026 and found that DAS "typically initialises after user login, then starts adding activities to be scheduled," and that on a current macOS it "submits at least 701 non-identical activities for scheduling." Time Machine, App Store update checks, Photos face and scene analysis, Spotlight maintenance, iCloud syncs, Siri data updates, log rotation, and dozens of third-party launch agents are all in that list.

Because it chooses the quiet moments, dasd is also the thing that wakes a sleeping Mac at night. The power management log records those wakes as requests from dasd, which is why people investigating a Mac that stirs at 3 a.m. end up here. That is expected behavior, and the jobs it starts, not dasd itself, are what use the CPU.

What normal looks like

dasd's own work is light. What people see in Activity Monitor is either dasd loading its list, or the jobs it launched running alongside it:

The overnight pattern is worth recognizing. A MacRumors poster in September 2026 described their CPU spiking "EXACTLY at midnight" with appstoreagent and dasd at the top; a reply pointed out that this pairing "is usually the App Store's automatic update check." That is dasd doing its job. The Mac is on, idle, probably on power, so the scheduler releases the queued work.

Why dasd is using CPU right now

Separate the two cases first: is dasd itself high, or are the processes it launched high? Then:

1. You just logged in or woke the Mac. dasd reloads its activities. A minute of CPU, then quiet.
2. It is a scheduled window. Midnight to early morning is common because Apple's update check and several maintenance jobs are daily and prefer idle time. The busy processes are appstoreagent, backupd, photoanalysisd or mds_stores; dasd is only coordinating.
3. Jobs keep failing and retrying. If a job cannot finish (the backup disk is missing, the Mac goes to sleep mid-run, there is no space), dasd reschedules it, and the retries can make the Mac look busy every hour. Fixing the job fixes dasd.
4. A macOS bug. Several releases have shipped with a dasd problem. Reports in late 2026 describe dasd on the first macOS 27 builds growing to tens of gigabytes of memory or sitting at 100 percent for days, alongside BiomeAgent and appstoreagent. One Apple Community reply in October 2026 was blunt: "In my case, it wasn't appstoreagent, just dasd." Those are fixed by updates, not by anything you do to dasd.
5. A third-party launch agent with a bad schedule. An app that registers an activity to run every few seconds keeps dasd evaluating constantly. Check Login Items & Extensions for anything you do not need.

Is it safe to quit dasd?

Force quitting dasd does no lasting damage, but it does nothing useful either. It is a root daemon that launchd restarts within seconds, and on restart it reloads all 700-odd activities and re-evaluates them, which is the same burst you saw at login. If the cause was a bug, the bug is still there. If the cause was scheduled jobs, they are still due. Some people report a temporary drop after a force quit; it is temporary.

You will also see advice to delete the PowerLog database or other folders under /private/var with elevated privileges, or to unload the daemon. Do not. Those folders are protected on modern macOS, the commands can leave the Mac in a worse state, and Apple's fix for each dasd bug has arrived as a point update anyway. Update, restart, keep it on power, and let the scheduled work finish.

Type any process name above to see which group it falls in. dasd is a "leave it, update macOS" process.

What to do, in order

1. Look at what else is busy

   Sort Activity Monitor by CPU. If appstoreagent, backupd, photoanalysisd or mds_stores are near the top with dasd, you are watching scheduled maintenance. Leave the Mac on power and it finishes; see those pages for how long each takes.

2. Install the latest macOS update

   Open System Settings, General, Software Update. If an update is waiting, install it. Every widely reported dasd bug, including the 2026 memory growth on early macOS 27 builds, has been addressed by a point release.

3. Restart to clear a stuck state

   If dasd itself is pinned or its memory is huge and no update is available yet, restart. That clears it until the next time; keep an eye on it after the restart.

4. Let overnight jobs finish once

   If the Mac is busy every night, it may be retrying a job that never completes. Leave it on power, lid open or connected to a display, for one full night. Jobs that finish stop being rescheduled.

5. Trim background items

   Open System Settings, General, Login Items & Extensions and turn off background items from apps you no longer use. Each one is an activity dasd has to track. Our background items page explains what is safe to switch off.

6. Stop the night wakes if they bother you

   In System Settings, Battery (or Energy), turn off Wake for network access. The Mac still runs its jobs while awake on power; it just stops waking from sleep for them. This is a preference, not a fix for a dasd bug.

When to worry

dasd cannot harm your files. The risk is battery drain, heat and, in the memory-leak case, a Mac that becomes sluggish after a few days of uptime. Use this timeline:

The tell for a leak versus normal scheduling is the trend across days, which Activity Monitor cannot show you. Safe to Quit keeps that history, so a dasd that grows a little every day stands out before the Mac starts swapping.