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GDB CS609 LAST DATE 23 - 1 - 2013

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koi to share kr de solution.................

plxxxxxxxxxxxxxxxxx share some points

Internal Fragmentation


dear allll  fellowss !!! kindly just tell me that   in first part  what is the impact of smaller block size on internal  fragmantation ..... does it  effect internal fragmentation or not if yes then howwww???????????????????

kindly reply soon ..

Please tell about the block size value  (multiple of two) what's this mean?

Block size considerations

When deciding on the block size for a file system, consider these points:

  • Supported block sizes are 256 KB, 1 MB, or 4 MB. Specify this value with the character K or M; for example, 4M. The default is 256K.
  • The block size determines:
    • The minimum disk space allocation unit. The minimum amount of space that file data can occupy is a sub-block. A sub-block is 1/32 of the block size.
    • The maximum size of a read or write request that the file system sends to the underlying disk driver.
  • From a performance perspective, set the block size to match the application buffer size, the RAID stripe size, or a multiple of the RAID stripe size. If the block size does not match the RAID stripe size, performance can be severely degraded, especially for write operations.
  • In file systems with a high degree of variance in the sizes of the files within the file system, using a small block size would have a large impact on performance when accessing large files. In this kind of system it is suggested that you use a block size of 256 KB and 8 KB sub-block. Even if only 1% of the files are large, the amount of space taken by the large files usually dominates the amount of space used on disk, and the waste in the sub-block used for small files is usually insignificant. For further performance information, see the GPFS™ white papers at 
  • The effect of block size on file system performance largely depends on the application I/O pattern.
    • A larger block size is often beneficial for large sequential read and write workloads.
    • A smaller block size is likely to offer better performance for small file, small random read and write, and metadata-intensive workloads.
  • The efficiency of many algorithms that rely on caching file data in a page pool depends more on the number of blocks cached rather than the absolute amount of data. For a page pool of a given size, a larger file system block size would mean fewer blocks cached. Therefore, when you create file systems with a block size larger than the default of 256 KB, you might want to increase the page pool size in proportion to the block size.
  • The file system block size must not exceed the value of the maxblocksize configuration parameter, which is 4096K.
  • NDMP backup prefetch is designed to work on files that are less than or equal to 1MB in size. NDMP backup prefetch will not work for a file system that has block size that is greater than 1MB.

kia kren gy???????????????????????????????

plzzzz some one help me?????????????????????????

may be help this


No it is not possible to have more internal fragmentation when the block size is smaller as internal fragmentation tends to decrease when memory model is implemented with smaller block sizes. In order to prove this we take the case (a) where we are allowed to use block sizes of multiple of 2. Let us consider we want to store 500 bytes. To store this with 512 bytes block only 1 block is needed and fragmented space is 12 bytes, but if block size is 1024 then 524 bytes will be unused and hence becomes fragment. In the third case it will be 1572 bytes using the formula (Number of blocks required*block size-data to be stored). Even if we use any block size it is not possible to have more internal fragments as smaller blocks. Hence as we have seen that the internal fragmentation tends to increase with the increase in block size so the given assumptions is refutable from the proof given in the case (a).



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