I am using a terabyte RAID5 with ext3 and created using mdadm, to store jpeg files on a rehdat 7.3 system. I need to write files to the RAID5 at the rate of 800 files per second, and each file is about 10-20 KB in size.
I have tried using data-writeback and the noatime options while mounting, and I am also using a stipe-size of 4MB (since 4MB was the max that mdadm would allow me), and i have passed -R stride=1024, and -b 4096 to mkfs.ext3 while formatting the RAID5.
Still, I keep getting "hiccups" every few seconds while writing the files.. mostly, these hiccups are at 5-second intervals, so it may suggest that the ext3 default commit interval is the culprit, and the effect has diminished after i changed the commit interval to 1 second in the kernel code, under
linux/fs/jbd/journal.c, the line changed was:
linux/fs/jbd/journal.c, the line changed was:
journal->j_commit_interval = (HZ * 1); // originally HZ * 5.
I have some questions at this point:
1. Is there any other way of modifying the commit interval? If possible I would like to take the commit interval modification out of the kernel and put it back in user level code..
2. Are there other things that I should try to optimize the write performance?
Thanks a lot in advance!!!
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