Explain why allowing backups to process read operations leads to sequentially consistent rather
than linearizable executions in a passive replication system.
What will be an ideal response?
Due to delays in update propagation, a read operation processed at a backup could retrieve results that are older
than those at the primary – that is, results that are older than those of an earlier operation requested by another
process. So the execution is not linearizable.
The system is sequentially consistent, however: the primary totally orders all updates, and each process sees
some consistent interleaving of reads between the same series of updates.
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All of the following statements about aligning text are true EXCEPT:
A) Alignment with the right edge aligned and the left edge uneven is called right-aligned. B) Alignment is mainly used in the first line of a paragraph. C) When words are evenly aligned on the left, they are left-aligned. D) Center alignment places text in the center of the line.
Which of the following is the default FTP port?
A. 21 B. 22 C. 23 D. 25