سوال ۲۲ کنکور ارشد مهندسی کامپیوتر ۱۴۰۱

Read the following passage (Passage 2) and answer the question.

To "recover" data from a bad sector, one would usually simply need to issue the Read Long command instead of the "normal" Read Sectors command. That is really it! It is so simple that any software developer who is familiar with hard drives can do it. And sure enough, more and more data recovery tools now come with a Bad Sector Recovery option. In fact, if a tool does not have a bad sector recovery feature, it automatically falls into a second-grade category.

Error detection and correction algorithms were implemented for a reason, which is exactly what the Read Long command does, disabling these algorithms and hence there is no way to prove that you get valid data. Instead, you get something, which may or may not resemble your customer's data.

Tests in our lab had shown that this approach allows you to get much more random bytes than anything else. Yes, there are cases where this approach allows recovering original data from a sector. But these cases are extremely rare in real data recovery scenarios, and even then, only a part of the recovered sector will contain valid data.

There are tools that claim better bad sector recovery. But they utilize a statistical approach, an algorithm where the tool reads the bad sector a number of times and then reconstructs the "original" sector by locating the bits that occur most often in the media or heads. While these tools claim this approach could improve the outcome, there is no evidence to back up the validity of such claims. Furthermore, re-reading the same spot many times while the hard drive is failing is a reliable way to cause permanent damage to the media or heads.

To verify data integrity, a hard drive __________.

1. prevents the data corruption through the use of some mechanisms
2. makes data more actionable by adding a layer of richness and complexity to it
3. proves that you get valid data by reading a sector with the Read Long command
4. will always validate it with error checking and correction algorithm