...
>The messages for an electronic mail system with several thousand users
>reside in a subdirectory of /var. The messages undoubtedly should have
>gone into a separate file system, even if the file system's mount point
>were in /var.
...
Thomas -
The next best alternative to a separate file system is a VIRTUALMountpoint,
allowing that subset to be treated as a separate Filespace, which will
substantially reduce the Active files list obtained from the TSM server
at the start of the backup, and thus reduce overhead on the client.
Email system backups can be a pain in general because of the high volatility
of the mail spools - particularly with contemporary spam levels - making for
a lot of retries...which tend to involve multiple files, per transaction size,
which dramatically slows down the backup. (But you do want user's mail backed
up, so you prevail.)
Here, for example, are stats for our busiest mail server system (of several),
which I programatically generate at the end of each backup and append to that
backup's log, via POSTSchedulecmd:
Number of tape mounts = 6
Number of users represented = 11,100
Number of file systems represented = 11
Number of files expired (deleted) = 329
Number of files backed up = 19,991
Number of files changed during backup = 1,044 632
occurrences of 1 retry
399
occurrences of 2 retries
8
occurrences of 3 retries
5
occurrences of 4 retries
Number of retries because file changed = 1,463
Number of retries, unchanged carry-alongs = 2,896
Number of skipped files (toomany changes) = 1
Number of files not found (transients) = 3
Number of bytes processed, incl. retries = 55,773,895,623 ( 51.94 GB)
Number of bytes sent to server stgpool = 52,482,139,412 ( 48.88 GB)
Number of bytes processed in retries = 3,291,756,211 ( 3.07 GB)
Number of directories backed up = 68
Number of homedir files backed up = 4,727 sum size =
12,567,977,512 ( 11.70 GB)
avg size =
2,658,764.02 ( 2.54 MB)
max size =
108,589,932 (103.56 MB, user ________)
Number of homedir Mail subdir files = 938 sum size =
1,907,026,661 ( 1.78 GB)
avg size =
2,033,077.46 ( 1.94 MB)
max size =
108,589,932 (103.56 MB, user ________)
Number of homedir IMAP "Sent Items" files = 1,365 sum size =
8,898,966,368 ( 8.29 GB)
avg size =
6,519,389.28 ( 6.22 MB)
max size =
80,990,198 ( 77.24 MB, user ________)
As you can see, the mail spool population remains fairly stable (filenames =
usernames) but the files themselves are continually in transition.
Richard Sims, BU
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