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These mechanisms are intended to prevent only accidental data loss or attacks by computer viruses. A determined user can easily circumvent them either by covering a notch with adhesive tape or by creating one with a punch as appropriate, or sometimes by physically altering the media transport to ignore the write-protect mechanism.
WORM drives preceded the invention of the CD-R, DVD-R and BD-R.An example was the IBM 3363. [1] These drives typically used either a 5.1 in (13 cm) or a 12 in (30 cm) disc in a cartridge, with an ablative optical layer that could be written to only once, and were often used in places like libraries that needed to store large amounts of data.
Copy-on-write can be implemented efficiently using the page table by marking certain pages of memory as read-only and keeping a count of the number of references to the page. When data is written to these pages, the operating-system kernel intercepts the write attempt and allocates a new physical page, initialized with the copy-on-write data ...
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Reserved: The block is the only copy of the memory, but it is still coherent. No write-back is needed if the block is replaced. Dirty: The block is the only copy of the memory and it is incoherent. This copy was written one or more times. This is the only state that generates a write-back when the block is replaced in the cache.
One source of lock failure occurs when buffered I/O has buffers assigned in the user's local workspace, rather than in an operating system buffer pool. fread and fwrite are commonly used to do buffered I/O, and once a section of a file is read, another attempt to read that same section will, most likely, obtain the data from the local buffer ...
A forensic disk controller or hardware write-block device is a specialized type of computer hard disk controller made for the purpose of gaining read-only access to computer hard drives without the risk of damaging the drive's contents.
An RW lock allows concurrent access for read-only operations, whereas write operations require exclusive access. This means that multiple threads can read the data in parallel but an exclusive lock is needed for writing or modifying data. When a writer is writing the data, all other writers and readers will be blocked until the writer is ...