I have just been thru rebuilding a server that had been suffering severe performance problems. I transferred the partitions to another hard drive, copying into freshly formatted filesystems. This made a HUGE difference in performance. One key directory structure stores email messages in an structure where there is a directory for each mail account, and the messages are stored in individual files. Some of these had grown to contain thousands of messages. A couple of weeks ago we went thru a purge, and deleted message files for inactive accounts, and were able to dump 75% of the files. Just doing that made a big performance improvement. Then a couple of days ago things got bad again, so I did the rebuild. My theory: these directories had obviously expanded to contain thousands of file entries. From the fact that just copying to clean filesystems made such a difference, I assume that deleting the files probably does nothing to remove the vacant entries and shrink the directories themselves. All this raises a few questions. . . (1) Is the assumption that directories don't compress when deleting files correct? How is this handled (in general terms)? (2) Is there any difference between ext2 and ext3? (3) Does the htree code change the picture any (even though I don't use it, and won't until it is production) ? (4) Is it possible that the directories themselves were fragmented? (5) After doing a "mkdir" to create a new directory, how many file entries can it hold before it would be expanded to accept another file? When a directory is expanded, how many additional file entries can be stored before needing another expansion? (6) Say I have a directory containing some files, then I delete some files, and finally I start adding files. Will new file entries use empty or vacated directory slots before expanding the directory? (7) I am aware of e2defrag (latest version I have found is 0.73). Does this program (or any other any tool) perform any directory optimization that would affect this problem? (8) If e2defrag would be helpful, has it/is it being brought forward to operate correctly with current (RH 8/9) systems? I see some warnings about blocksise restrictions, etc. (9) In designing new systems, are there some useful guidelines about the maximum number of files that can exist in a single directory without significant performance loss? I am interested in ext2, ext3, and htree. TIA, A. Becker _______________________________________________ Ext3-users@redhat.com https://www.redhat.com/mailman/listinfo/ext3-users
