Wednesday, 5 September 2012

Data recovery time in different filesystems


In FAT filesystem, structures describing directories are spread over the area of data and therefore mixed with the contents of files. If a directory is deleted, easily accessible information about its location is no longer available. In this case it is necessary to do a full scan of the data area to be sure that all the directories are found. Thus, data recovery time on FAT is proportional to the size of the disk and is mainly determined by the time needed to read the entire disk.

NTFS stores metadata densely at more or less known location; when recovering data from an NTFS volume, data recovery software can just look at this small area rather than scan the entire disk. Data recovery time on NTFS is mainly limited by computing resources required to recreate the file table. The total time doesn't depend on the disk capacity but it depends on the number of files actually stored on the disk.

ReFS again spreads its metadata over the disk, mixing it with the content of files to save disk head movement during read/write operations. From the recovery point of view, it means that you need to scan the entire disk even if you just want to find a single deleted file.

From the stability point of view, the filesystem with the spread storage wins over the filesystem with the localized storage of metadata. However, it doesn't apply to FAT filesystem since file allocation tables are stored compactly in the beginning of the volume.

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