File System Anomaly Notification: Delayed Write Error

Conditions for Delayed Write Error Occurrence: Internal drive disconnection due to some cause

This error often occurs due to compatibility issues or malfunctions with external devices, but it can also occur when internal drives are disconnected for any reason. Even when external devices are not connected, you might have encountered a phenomenon where a “Hardware Removal” notification suddenly appears in the bottom right corner, and then mysteriously disappears after a certain period. If this notification appears for internal drives, it’s definitely a sign of a “failure” or “compatibility issue.” In any case, your data is at risk, so it’s essential to back up immediately.

“Loss of Delayed Write Data” notification remains. What does this mean?

These errors lead to “file system corruption” when the drive is disconnected while writing data in the background, due to cache issues. If you inadvertently disconnect the drive during data writing and encounter such an error, you should proceed as follows. “Safe removal” is necessary to complete asynchronous writing. Internally, the number of writes is tracked, and the drive becomes removable when this count reaches zero.

“Loss of Delayed Write Data” notification remains. What does this mean? Part 2.
「遅延書き込みデータの紛失」の表示が出たままとなる。これって……? その2です。

The drive transitions to a “surprise” state, and then the driver notifies Windows, resulting in a “Delayed Write Error.” In such cases, connect the problematic medium as an external device to check if important files can be read. First, back up important data. It’s crucial. Before attempting repairs, always back up your data first. Run Check Disk without options to assess the file structure. The key is to evacuate important data first. Perform the inspection-type Check Disk last. If problems are found, run Check Disk again.

If errors accumulate, eventually all files become unreadable. Prioritize backups if the drive’s condition is uncertain. If the data is saved, there’s hope. Using Check Disk after file system damage can cause “further corruption.” This is because elements necessary for reconstructing the file system (e.g., records inside the MFT being destroyed by bad sectors) are significantly lacking, making it impossible to fill these gaps. Corrupted records are stored in a “hidden folder,” and serial numbers replace lost filenames.

If safe removal is not possible, shut down the system.

It’s a tricky situation when you can’t remove a drive that’s in use. In such cases, as it’s being used by other processes, a shutdown is necessary. Although inconvenient, shut down and safely remove the drive.

Regarding Gradual Data Loss:

1, FAT32/exFAT:
Initially, some folders disappear, gradually increasing until access to the entire drive is denied.
1, FAT32/exFAT:
2, NTFS:
Access to some folders becomes impossible, blocking access to internal files. Access to “some folders” is unimpeded, but other areas start to be affected. The cause is “accumulated errors” or “unreadable/write-protected sectors.”
2, NTFS:

Data Loss in HDD/SSD Cache
HDD / SSD キャッシュのデータ損失

If power is lost during access, priority is given to moving the head to safety using the remaining power on the board. At this time, if cache data remains, it needs to be written back. However, this evacuation takes priority over the power supply, leading to cache disposal.

Data Loss in SSD/NVMe Cache
SSD/NVMe キャッシュのデータ損失

Often, the OS separately caches data, significantly reducing read/write times. However, before removal, the cache’s contents need to be written back to the drive, necessitating “safe removal.” From Windows 10 onwards, considering the risk of data loss, “OS-level caching” has been disabled by default. SSD caches are considered safe from power loss due to low power consumption and the absence of moving parts.

Conditions for Delayed Write Error Occurrence: Forced disconnection of external drives
「遅延書き込みエラー」が生じてしまう条件: 外付けのドライブが強制解除

Even without any user action, involuntary disconnection of external drives often leads to “data loss.” This usually indicates drive failure, preventing normal operation. If you encounter this situation, calmly turn off the power, then turn it back on, and immediately perform a “backup” once connected. If the drive behaves oddly during this process, turn off the power immediately. If the data is important, consider a data recovery service at this point. Repeated attempts can scratch the platter, making data recovery more difficult.