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Old 05-30-2005, 05:21 AM   #1
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performace impact after establishment of a large file

After creating a large file (+1.2GB) on a device presented from a cx500 the response time for accessing any other device presented from the cx500 increased to 30 sec. A script which does nothing more than dd to each device is used for the test. The environment uses RH3 update 4 with (2x)Qlogic HBA's and has tried driver versions 7.0.3 and up. Multipathing software - such as PowerPath has not made any difference as the symptoms manifest themselves whether installed or not. The use of raw devices is also part of the overall environment. An example, this is a line from the test script; dd if=/dev/raw/raw1 of=/dev/null bs=512 count=1
A reboot of the host clears up the symptoms and device access returns to a time of about 2 secs for each line in the test script. Would speculate the kernel holds some type of meta data from a large file creation that may be the underlying cause for this problem. has anyone encountered this?
Old 05-31-2005, 03:29 PM   #2
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What file system are you using?
Old 06-01-2005, 02:38 AM   #3
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These are raw devices.
Old 06-01-2005, 02:41 AM   #4
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I'm hearing now that there may be a bug in the Qlogic driver, but I don't have any verification for this symptom to a 'bug'.


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