The drive which you are going to sell or dispose of may still contain either some personal data. This data is to be removed off the disk before getting rid of it.
As far as software is concerned, there are several programs both free and paid that can overwrite the information by either 0s or random noise. Once overwritten, the data is irreversibly deleted.
To obtain the same result yourself as with the secure erase software, just format the hard disk and load it fully with some stuff you don't care about (similar to multiple copies of House MD videos). Once the big file fits no more, continue adding smaller files. You can also do this with an USB box. On modern full encryption disks, just changing a password gets you the same result as after a secure erase.
Thursday, April 7, 2011
Saturday, March 26, 2011
Before building an array
When building some really big data storage, you should keep in mind the following concerns:
Taking into account the above then it is needed to decide if you try to build your own storage unit or just order off-the-shelf data storage. If you choose the latter option then consider at least this one of RAID tips.
If you decide to build your own RAID then check all of the www.raidtips.com.
- array size
- fault-tolerance
- speed
- amount of money you are going to spend
Taking into account the above then it is needed to decide if you try to build your own storage unit or just order off-the-shelf data storage. If you choose the latter option then consider at least this one of RAID tips.
If you decide to build your own RAID then check all of the www.raidtips.com.
Sunday, March 6, 2011
Does a RAID decrease access time?
Storage device performance is described by:
Access time is more tricky. Access time in a regular hard disk includes the time needed to move a read head above the target track (seek time) and the time which is needed a hard disk to bring a sector under a read head (rotational latency).
Regardless of the number of member disks in RAID 0 it may occur that the cache doesn't have a requested sector which in turn is the furthest from the read head. If this sector is needed the access time is the same (not better) as in case of a single drive. If you are willing to improve random access time you should get rid of rotational hard drives and get an Solid State Drive instead.
- access time
- throughput is sustained average speed of data transfer.
Access time is more tricky. Access time in a regular hard disk includes the time needed to move a read head above the target track (seek time) and the time which is needed a hard disk to bring a sector under a read head (rotational latency).
Regardless of the number of member disks in RAID 0 it may occur that the cache doesn't have a requested sector which in turn is the furthest from the read head. If this sector is needed the access time is the same (not better) as in case of a single drive. If you are willing to improve random access time you should get rid of rotational hard drives and get an Solid State Drive instead.
Saturday, February 12, 2011
The data file recovery
There exists a variety of tools doing the repairs or data extraction from a given file type, like DOC/DOCx, ZIP and so on. The file recovery is actually one more recovery type, similar to photo recovery which was mentioned earlier.
The file recovery software may be useful if the file got damaged because the file data was not fully written to a drive, say, because of the power failure during the write. Or because the program working with the file crashed before completing the write. Should this happen, the actual file content (or a worthwhile part of it) might still be written to the file.
Practically, it is pointless to apply such software to "fix" files which data recovery software found on the damaged drive. The data recovery process, such as the one used to recover RAW file system, typically either gets OK files, or the files are fully damaged, not containing any trace of original data. If the files do not open in their respective programs after a data recovery, this means most certainly no subsequent fixing applied to these files can restore them because the useful data is just not there.
The file recovery software may be useful if the file got damaged because the file data was not fully written to a drive, say, because of the power failure during the write. Or because the program working with the file crashed before completing the write. Should this happen, the actual file content (or a worthwhile part of it) might still be written to the file.
Practically, it is pointless to apply such software to "fix" files which data recovery software found on the damaged drive. The data recovery process, such as the one used to recover RAW file system, typically either gets OK files, or the files are fully damaged, not containing any trace of original data. If the files do not open in their respective programs after a data recovery, this means most certainly no subsequent fixing applied to these files can restore them because the useful data is just not there.
Monday, January 10, 2011
Why are only the thumbnails are sometimes recovered?
More often than not while recovering digital photo files, typically off a memory card, the small image previews, called thumbnails, are recovered successfully, while high-resolution images themselves are damaged.
This behavior is explained by "file fragmentation". The fragmentation is said to occur when the file is stored on the disk in more than one non-contiguous blocks. The sketch explaining the process can be found at the Photo Recovery Limitation page.
The FAT or FAT32 filesystem is most likely to be used on a memory stick or a thumb drive.
Once the file gets erased on the FAT filesystem, the only information that is still available is how to locate the 1st fragment. Any subsequent blocks cannot be recovered.
Thumbnail is not large and placed at the beginning of the file, therefore the thumbnail is usually extracted OK, and still the high resolution image is garbled. Of all the data recovery types, this limitation affects mostly digital photo recovery and unformat on FAT.
This behavior is explained by "file fragmentation". The fragmentation is said to occur when the file is stored on the disk in more than one non-contiguous blocks. The sketch explaining the process can be found at the Photo Recovery Limitation page.
The FAT or FAT32 filesystem is most likely to be used on a memory stick or a thumb drive.
Once the file gets erased on the FAT filesystem, the only information that is still available is how to locate the 1st fragment. Any subsequent blocks cannot be recovered.
Thumbnail is not large and placed at the beginning of the file, therefore the thumbnail is usually extracted OK, and still the high resolution image is garbled. Of all the data recovery types, this limitation affects mostly digital photo recovery and unformat on FAT.
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