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RE: Arch configuration -- I/O stuck

From: Steve Adams <>
Date: Wed, 31 Oct 2001 19:53:24 -0800
Message-ID: <>

Hi Pablo,

The 'ls' is probably getting stuck because the I/O is very slow and file system metadata writes are stuck in the I/O
queue while locks are held on the file system metadata pending the completion of those writes.

The problem could be that you are saturating the cache allocations for the EMC LUNs containing your archive destination
file system. See the answer at for a bit about the EMC cache allocation
policy. To solve the problem you can use LVM to stripe a large number of small LUNs together so as to increase the total
amount of cache available for the archival writes. You would also do well to avoid RAID-S of course!

@ Regards,
@ Steve Adams
@ - For DBAs
@ - For all

-----Original Message-----
Sent: Thursday, 1 November 2001 5:45
To: Multiple recipients of list ORACLE-L

Hi list,

  Oracle 7.3.4
  log_archive_buffer_size=32 (redo log blocks = 1K)   log_archive_buffers=4
  Filesystem based (no direct I/O)

  I've been detecting that my box gets stucked eventually for some time.
  When this happens I can't do even a "ls" (it actually executes it but it takes a long time).   If I check my cpu with TOP, I see 47% idle time and there's no process monopolizing the CPU.   But when I check disk activity with sar -d I see that one disk is 100% busy and it's avwait+avserv > 1000 ms. The other disks are fine.
  I then check disk activity with Glance and I can identify the process that's writting/reading on this disk is: ARCH (ARCH is writting a 1.9 GB redo log.)

  So here are my doubts:

      1)If only one disk is saturated (I've got about 30 disks in this box (a SYMMETRIX array) with some controllers), why does the whole box get stucked? why are even other applications connected to other instances running on this box affected? (may be because the HP-UX LVM system gets saturated???)

     2) What can I do to avoid this problem?, (reduce log_archive_buffers parameter may be, or increase log_archive_buffer_size)

help me on this

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Author: Steve Adams

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Received on Wed Oct 31 2001 - 21:53:24 CST

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