data from blktrace: read speed V.S. write speed

Applications Filesystems, Disks and Memory
1

I analysed disk performance with blktrace and get some data:
read:

  8,3    4     2141     2.882115217  3342  Q   R 195732187 + 32 [cat]
  8,3    4     2142     2.882116411  3342  G   R 195732187 + 32 [cat]
  8,3    4     2144     2.882117647  3342  I   R 195732187 + 32 [cat]
  8,3    4     2145     2.882118965  3342  D   R 195732187 + 32 [cat]
  8,3    4     2149     2.884145702     0  C   R 195732187 + 32 [0]

write:

  
  8,3    4    43622     5.305507398  3436  Q   W 17805895 + 8 [bash]
  8,3    4    43623     5.305508277  3436  G   W 17805895 + 8 [bash]
  8,3    4    43624     5.305508574  3436  I   W 17805895 + 8 [bash]
  8,3    2      414     5.306695591     0  D   W 17805895 + 16 [swapper]
  8,3    2      418     5.307020642     0  C   W 17805895 + 16 [0]

And, d2c time of one read request is 0.002026737s. On the other hand, d2c time of one write request is 0.000325051s. It show: read time > write time. Is it right? why? I have no idea.

2

The write operations are almost certainly getting cached somewhere, most likely in the kernel page cache or the cache on the disk(s) themselves depending on your OS and hardware setup.