虽然我们大多数人不需要随身携带外置硬盘，但有些人可能需要随身携带。考虑到这一点，明显的温度差异会对硬盘产生负面影响吗？今天的超级用户问答帖子回答了一位忧心忡忡的读者的问题。

今天的问答环节是由SuperUser提供的，SuperUser是Stack Exchange的一个分支，是一个由社区驱动的问答网站分组。

图片由Gillware Data Recovery（YouTube）提供。

问题

超级用户读者misha256想知道外部USB硬盘是否有内部冷凝的风险：

Apparently, you can kill a USB hard-drive by moving it from a cold temperature environment to a warm one and powering it up (the killer being internal condensation).

How real is the risk? What kind of temperatures are we talking about? I do not want to waste time acclimatizing my hard-drive every day if it is not necessary. Are there technologies or soluti*** available to mitigate the risk?

Surprisingly, I have found nothing useful on the Internet that provides satisfactory answers to my questi***.

外部USB硬盘是否存在内部冷凝的风险？

答案

超级用户贡献者harrymc为我们提供了答案：

Condensation is a real danger for hard-drives. You can see in a real-life YouTube dem***tration by a data-recovery specialist what a hard-drive looks like when taken out of a freezer and briefly turned on (it is full of scratches):

Such scratches could possibly damage the hard-drive to a point where even a data-recovery specialist would be unable to recover the data. A Control Data (later Seagate) factory packaging manual for hard-drives says:

• If you have just received or removed this unit from a climate with temperatures at or below 50°F (10°C), do not open this container until the following conditi*** are met, otherwise condensation could occur and damage to the device and/or media may result. Place this package in the operating environment for the time duration according to the following temperature chart.

It seems that dangerously low temperatures start when a computer is brought in from temperatures below 50°F (10°C) into a room-temperature area and it may need several hours for acclimatization. This long time is explained by the fact that in a mechanical hard-drive, the head is supported by airflow entering through special air-intakes. These intakes are heavily filtered against dust, but not against humidity. They are also **all enough that it slows down the evaporation process of internal humidity.

You could possibly minimize the acclimatization time by wrapping the disk in watertight plastic while it is acclimatizing in order to reduce the humidity that would enter via the air-intakes. You should allow for some drying-off time after unwrapping the disk (for the humidity in the air already contained inside the disk).

This is not the only danger, as explained by data-recovery specialist ReWave Recovery:

• A hard-drive is at risk for sudden temperature changes including overheating and condensation.
• A sudden change in temperature that causes condensation inside the hard-drive can cause the material on the platter to evaporate which causes the read/write heads to stick to the platter and stop it from rotating.
• Overheating can also be an issue. Overheating can cause the platters to expand which makes the read/write heads travel farther to read the data. The expansion of platters can cause friction which can lead to a head crash.

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