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journal tuning



  Hello,

  Is there some document about ext3 performance tuning and choosing
the right type and size of journal? Except RedHat's white paper.

  From what I read I understood that for typical operations
data=ordered is prefered. For the cases when there are many writes
not appending to files data=journal is the choice. And if I want to
get the most performance or in case where program is doing journaling
itself (Oracle) - data=writeback is the answer.

  But what about the size of the journal? The only clues I found is
that data=journal journal should be the size ~ 5 seconds worth of
writes to the disk. And that other types journals are typically
sized enough by default.

  System is Redhat 7.3.

  Thank you,

  Mindaugas

  P.S. What tool can show data flow per disk device? In my case
vmstat shows total but iostat and sar shows nothing about disk I/O.
SCSI - Compaq CISS Driver (v 2.4.30).






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