1. Four symptoms that look identical from the phone

"The SD card isn't working" arrives with the same phrasing every time, but the underlying faults are different and only one of them is the card.

Each row has a different fifteen-minute fix. Working them in order is far cheaper than replacing a card that was never the problem.

2. The three-layer model for on-camera recording

Dahua's camera firmware separates storage into three surfaces, and each has to agree with the other two.

Layer one — the card. Is it detected, writable, and formatted? This lives under Storage.

Layer two — the plan. When should the camera record, and under which event type? This is the Time Plan tab under Record.

Layer three — the control. Is recording mode on? This is the Record Control tab, and it is where most silent failures live.

There is a fourth variable that is easy to forget because it looks like a detail: the storage method that decides which media receives the video. If a site has both a card and an FTP target configured, the storage method determines where files actually land, and "nothing on the card" can simply mean the card was not selected.

3. Layer one: read the card page properly

Open the camera's web interface and go to Storage. The page shows the local SD card information and gives four controls that matter.

Read-Only / Read-Write. This is a mode switch, not a status label. A card left in read-only plays back existing footage perfectly and records nothing new. On a support call this is the setting to check first, because the camera looks completely healthy: the card is present, the capacity is correct, and old video plays.

Hot Swap. This prepares the card for removal without powering down. Using it is good practice, but it is not a fix for a stuck camera — it is a safe-eject control.

Format. Formats the card. Everything on it is destroyed, so confirm with the customer before pressing it. Formatting is the correct action for a new card and for a card that shows an implausible capacity.

Capacity display. If the reported size looks wrong — far smaller than the label says — the manual explains why: cameras may format the card to a private file system, which improves multimedia read and write performance. Reading that card on a PC can show a much smaller capacity than nominal, and this is expected rather than a fault. To read the footage on a computer, the manual points to a DiskManager utility from the Toolbox rather than a normal card reader.

3.1 What is actually on the card

Understanding the file layout prevents a whole category of false alarms, because the card does not look like a folder of videos when you take it out.

The camera writes files in packs whose length is set by Max Duration on the Record Control page. With the default of thirty minutes, a day of continuous recording produces forty-eight files. Each file carries its own index entry, and the card also holds a database that the camera uses to find footage quickly. That database is why a PC cannot always read the card directly, and why the manual points to a vendor utility rather than a card reader.

When the card fills, the camera overwrites the oldest material. This is normal and is what makes continuous recording sustainable on a fixed-capacity medium. The consequence for the customer is that retention is a rolling window: the oldest footage disappears silently, and nobody notices until they look for something from three weeks ago. Setting a realistic expectation at handover — "this holds about eleven days at this quality" — prevents that conversation entirely.

File size also affects recovery. A long pack duration means fewer, larger files, which is convenient for exports but means a corrupted index can cost more footage at once. A shorter pack duration limits the blast radius. On sites where footage is legally important, shorter packs plus regular exports is the safer configuration.

Finally, the card stores not just video but event metadata. When AI rules were enabled during recording, playback can overlay the rule and detection box. If the rules were not enabled at the time, the overlay will not appear later — the metadata was never written. That is why "the AI box is missing in playback" is sometimes not a bug but a record-time configuration difference.

4. Layer two: build a record plan that matches intent

Open Record on the home page and select the Time Plan tab. You get a weekly grid with six periods per day, and three event types drawn as coloured bands.

Scheduled (green) is continuous recording for the drawn window. Motion (yellow) writes when the camera's motion detection triggers, and is also the band that intelligent events use. Alarm (red) responds to alarm input or alarm-type events.

Two operational details decide whether the plan behaves as the customer expects.

Overlaps are allowed, and they are not additive. A period with both green and yellow drawn does not record twice as much; the camera writes when either condition is satisfied. What matters is that the band exists at the moment of interest. An empty band at 10:00 means nothing is written at 10:00 regardless of what is configured elsewhere.

Holiday overrides the normal plan. The manual is explicit: when a day is marked as a holiday and the holiday schedule differs from the general setting, the holiday setting takes priority. Sites that mark public holidays and then wonder why the pattern changed on those dates are seeing this rule work correctly.

The Copy control next to each day is the difference between a five-minute plan and a forty-minute one. Draw Monday correctly, copy to the remaining days, then adjust Saturday and Sunday if the site closes.

5. Layer three: Record Mode is the switch people miss

Open Record and select the Record Control tab. This page holds four settings, and the third one is the reason most "SD card not recording" tickets exist.

Record Mode. The manual describes the two useful states plainly: Manual starts recording immediately and continuously, while Auto records according to the configured record plan. Off records nothing. A camera shipped or reset will often sit at a state that is not what the installer assumed, and a plan without Auto produces silence.

The practical rule is simple: if the customer wants the plan respected, set Auto. If they want continuous recording regardless of plan, set Manual — but understand that Manual ignores the plan entirely, which is usually not what a site with a considered schedule actually wants.

Max Duration. The file packing length, adjustable from one to one hundred and twenty minutes. Longer files mean fewer files and simpler exports; shorter files are easier to scrub and to transfer over a weak link. The default of thirty minutes is a reasonable compromise for most sites.

Pre-Record. Zero to five seconds of buffered video before an event. This is what makes a motion clip start before the person appears. If clips consistently "start too late", this value is the first thing to check, and it is also why a camera with pre-record set to zero appears to miss the beginning of every event.

Record Stream. Choose main stream for image quality or sub stream for card longevity and storage economy. On a card-sized volume, sub stream can multiply retention by a large factor — at the cost of detail when the footage is reviewed.

5.1 Auto or Manual: match the mode to the site

Because both modes record, choosing between them is a design decision rather than a preference. Getting it wrong produces either wasted capacity or missing hours, and the customer experiences both as "the camera is unreliable".

Choose Auto when the site has a defined operating pattern: a shop open 09:00–21:00, a clinic with fixed hours, a warehouse running one shift. Auto plus a plan that covers the busy window records what matters and leaves the quiet hours to motion events. It is also the only mode that lets a holiday schedule take effect, because holiday behaviour is an override of the plan.

Choose Manual when the requirement is completeness and the site has no predictable pattern: a construction compound, a remote gate, a temporary installation, or any location where "we need everything, always" is the actual requirement. Manual records continuously and ignores the plan, which is exactly the point — and exactly the reason it should not be used on a site with a considered schedule.

A practical hybrid that works well on card-limited installations: Auto with a scheduled band during high-value hours and a motion band during the rest. The card then holds a long window of detail where it matters and a long window of events where it does not, instead of a short window of everything.

Whatever the choice, write it on the handover sheet. The next technician should not have to infer the recording philosophy from the timeline.

6. The storage method: where the video actually goes

Under Record > Storage the camera lets you choose the storage method for recorded video. This is a routing decision, not a capacity decision, and it explains a specific confusion: a camera can be recording correctly while the card stays empty because the selected method points somewhere else.

Where multiple targets exist, confirm that the card is among them. On sites that also upload to a server, verify which media the requirement actually depends on. A customer who expects card footage during a network outage needs the card to be a local target, not a fallback.

This is also the page where retention expectations should be set honestly. A card records until it fills, then behaves according to the device's overwrite behaviour. There is no "thirty days" guarantee on a 128 GB card with four cameras at full quality, and the arithmetic does not care what the sales conversation promised.

7. Prove it: use the playback search

Open Record > Search Video, pick the channel, the record type and the time range. The manual describes the useful tell: dates with blue dots are days that have recorded video. That single visual answers most "is it recording at all" questions in five seconds.

The record type filter separates All, General, Event, Alarm and Manual. Choosing Event opens a sub-list that includes motion detection, video tampering and scene changing. If a customer says "motion isn't recorded", search with the Event filter before touching any configuration — the footage may be there under a type nobody selected.

When you find a clip, the playback page supports digital zoom, AI rule overlay (only if rules were enabled during recording), frame stepping, snapshot and clipping. Clipping is the right way to hand footage to a customer: it produces a file with a defined start and end rather than a phone recording of a monitor.

7.1 When footage exists but the timestamps lie

The most misleading playback failure is not an empty card. It is a card full of footage filed under the wrong times, which makes a working camera look broken and a broken one look fine.

Footage timestamps come from the camera's clock. If the device is set to the wrong time zone, every clip is offset by hours, and a search around 14:00 finds nothing while the footage sits at 21:00. If the clock drifted because NTP was never configured, the offset grows slowly, so the problem appears weeks after commissioning and looks like data loss.

Two habits resolve it. First, before searching, note the camera's own displayed time and compare it with a trusted reference; a mismatch of more than a minute on a recording device is worth fixing regardless of the current ticket. Second, when a customer reports a specific incident, search a window considerably wider than their estimate — a six-hour range instead of a one-hour range. Footage that appears missing is frequently just outside the assumed window.

Time zone configuration also interacts with daylight saving. A camera pinned to the wrong zone, or with daylight saving handled incorrectly, will shift its entire library twice a year. If playback gaps appear in the spring and autumn and nowhere else, this is the likely cause and the fix is in the device time settings rather than in storage.

8. Let the camera tell you when the card fails

Cameras with cards support an exception detection page under Event > Exception > SD Card Exception. It covers three conditions, and each one is worth enabling on any site where the footage matters.

No SD card. Fires when detection finds no card. This is the alarm that catches a card that was never seated, was removed for copying and never returned, or has failed to the point of not enumerating.

Low SD Card Space. You set a free-space threshold; when the card falls below it the alarm triggers. This is the early warning that prevents the "it stopped recording last Tuesday" conversation, because it fires while there is still time to react.

SD Card Error. Fires on a detected card fault. Combined with the other two, it turns silent storage failure into a notification with a linkage you choose — email, alarm output, or a recording marker.

All three feed the same alarm linkage mechanism, so the notification path is configured once and reused. A site that has never enabled these three toggles is relying entirely on somebody noticing missing footage, which is exactly the failure mode this guide exists to prevent.

8.1 A two-minute triage before the twelve

Most calls can be narrowed to one layer in under two minutes with three observations. Doing this first means the twelve-cause list is used to confirm a hypothesis rather than to fish.

Observation one: does the Storage page show a card with plausible capacity? If not, the fault is physical or formatting. Nothing downstream matters yet.

Observation two: does playback show a blue dot for today? If today is marked and yesterday is not, the camera records but recently stopped — a capacity or plan change. If no day is marked at all, the plan or the mode is off.

Observation three: what does Record Mode say? Auto and Manual both record; Off does not. This single field resolves the majority of "nothing is being written" reports before any other page is opened.

Three answers, three layers. Only when all three look correct is it worth investigating storage method, event linkage or medium failure.

9. The twelve causes, in check order

1. Record Mode is Off. Plan present, card healthy, nothing written. Check this before anything else.

2. Record Mode is Manual and the plan is expected to apply. Manual records continuously and ignores the plan, so event bands may not appear where the customer expects.

3. Card is set to Read-Only. Playback works; writing does not.

4. Card is new and unformatted. Detected, unusable.

5. Card was formatted on a PC. The private file system is gone; reformat on the camera.

6. The plan bands are empty for that channel and day. Nothing drawn means nothing recorded.

7. Bands exist but only for a window outside the incident time. Check the timeline against the reported time rather than against assumptions.

8. Motion is expected but the record type band is scheduled-only. Drawing green does not enable yellow.

9. Storage method does not include the card. Video is going somewhere else.

10. Card is full and the device stops rather than overwrites. Recording ended quietly at the point of fullness.

11. Card has worn out. Cards in constant-write service fail; a card that works for stills can fail under continuous video. This is common in cameras that have run for a year or more at high bitrate.

12. The camera's clock is wrong. Files exist but sit at timestamps that make them look missing. Search a wider range before concluding nothing was written.

10. Choosing a card that survives the job

The manual specifies the interface and the file system behaviour, but it does not pick a card class for you. That choice determines how long the installation lasts.

Match the endurance rating to the workload. A camera writing continuous 4MP video performs a very large number of write cycles per day. Cards intended for dashcams or surveillance are rated for that pattern; general-purpose cards are not, even when their headline capacity and speed look superior. The failure mode is not a dramatic death but a slow degradation: sectors fail, writes slow, and eventually the card stops accepting data while still enumerating.

Size for retention, not for headline numbers. Two cameras at moderate bitrate and motion-only recording will fill a card far slower than six cameras recording continuously. Use the recorder or the camera's own estimate tools rather than intuition, and be conservative — cards lose usable capacity as they age.

Prefer cards from known supply chains. Counterfeit capacity is still a real problem: a card that reports 128 GB and holds 32 GB will overwrite its own oldest files in a way that looks like a retention bug. If capacity readings behave strangely, test rather than trust the label.

Replace on a schedule. For critical sites, treat the card as a consumable with a service life rather than a permanent component. Logging the install date on the handover sheet makes it possible to replace proactively instead of after an incident that cannot be reviewed.

10.1 Reading the warning signs before failure

A failing card rarely fails all at once. It degrades through a sequence that is observable if anyone is watching, and the three exception alarms above are the instrument for watching.

Increasing write errors. The card still records but begins dropping segments. On playback this shows as small gaps that move around, not as a clean stop. If a customer reports "the video skips" and the card is old, suspect the medium before suspecting the network.

Slower formatting and mounting. A card that takes noticeably longer to format than a new one of the same type is telling you it is struggling. Comparing against a known-good card of the same model is the fastest test.

Capacity that shrinks. Bad sectors are retired by the controller, so usable capacity can fall over time. A card reporting meaningfully less than when it was installed is on its way out.

Spontaneous read-only state. Many cards drop into a write-protected condition as a final protective measure when internal failure is detected. This is why "it suddenly became read-only by itself" is a classic end-of-life symptom rather than a configuration change.

None of these require specialised tools to notice; they require someone to look at the exception log occasionally. On managed sites, a monthly glance at the three SD card exceptions plus a spot check of playback is enough to catch the majority of failures before the footage matters.

11. Commissioning checklist

The last step is the one most often skipped: write down what you configured. Card size and install date, the chosen record mode, the plan pattern, and the measured retention in days. That page turns the next visit from an investigation into a comparison, and it is the difference between a site that stays reliable and one that gets re-diagnosed every few months.

12. When the recorder is the real destination

Many cameras with cards are also recording to an NVR, and the card is a backup path rather than the primary one. That changes the troubleshooting order: if the card is fine but the recorder has nothing, the camera-side plan is irrelevant and the NVR storage is the place to look.

The distinction matters for customers too. Footage on the card survives a network failure and a recorder failure; footage on the recorder survives a card failure. Sites that need continuity in both directions should configure both, and should test both. A surprising number of installations have one path configured and are assumed to have two.

If the recording chain ends at a recorder rather than a card, work through disk state, recording schedule and record mode on the recorder — the same three-layer logic, applied one device upstream. Our NVR recording troubleshooting guide covers that path in detail, including the disk-full and Motion & Alarm traps that produce the same "nothing recorded" complaint.

13. FAQ

Why does the card show far less capacity on my PC? The camera formats to a private file system for better multimedia performance. Read it with the vendor DiskManager utility rather than a normal card reader, and do not reformat on the PC.

Card is installed and visible, but nothing records — where do I start? Record Control. Confirm the mode is Auto (or Manual if continuous recording is intended) and press Apply.

Does Manual mode follow my schedule? No. Manual records continuously; Auto follows the record plan.

Why do clips start after the event? Pre-Record is set to zero. Increase it to buffer video before the trigger.

Why did recording stop after a few weeks? Usually the card filled and the device stopped, or the card is worn. Enable Low SD Card Space so you hear about it before the customer does.

Can I record to both the card and a server? Yes, subject to the storage method configuration. Confirm which target the requirement depends on.

Playback shows blue dots only on some days — is the card failing? Not necessarily. That pattern usually means the plan only covers those days, or the camera was powered down. Check the plan and the device time first.

How long should a card last? It depends on bitrate, camera count and write cycles. Surveillance-rated cards in continuous service are consumables; log the install date and plan replacement.

13.1 Multi-camera sites and the write budget

Card failures cluster on busy sites, and the reason is arithmetic rather than bad luck. A card has a finite number of write cycles, and every camera on the site draws from its own budget independently.

Two cameras recording continuously at high bitrate can consume a card's endurance in a fraction of the time one camera would. Adding a third doubles the write load again. When a site reports "the cards keep dying", the useful questions are how many cameras write continuously, at what stream, and for how many hours per day — not which brand of card was used.

There are three levers, in order of effect. Move continuous recording to the sub stream where detail is not required. Replace part of the continuous window with motion recording so the card writes only when something happens. And size the card for the actual write load rather than for a headline number that assumes a lighter duty cycle.

The same logic applies to the expectation conversation. A customer who is told "this card holds thirty days" on a four-camera site will be disappointed in three weeks, and the disappointment will be aimed at the installer rather than at the arithmetic. Giving a realistic number at handover — and writing it down — converts a future complaint into a documented design decision.

For sites that genuinely need long retention and cannot accept card-sized volumes, the right answer is not a bigger card but a recorder. Cards are excellent for edge resilience and short-window evidence; they are the wrong tool for multi-week archives across many cameras.

14. Sources

• Dahua Network Camera Web 5.0 Operation Manual V1.3.1 — §6.5.2.1 SD Card Exception, §6.6 Storage, §10.1 Playback, §10.2 Record Control, §10.3 Record Plan, §10.4 Storage
• Dahua Technology — documentation portal

If you are specifying cameras for a site where local recording matters, the Dahua network camera range lists card-supported models, and the matching accessories line covers mounts, power and storage media. For installations that also rely on PTZ coverage, the PTZ collection is the right starting point.

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