Re: .ini settings for ADD KEY to 30Gb table on 96Gb machine?

[Rick James]

You are doing most things 'right'.

I'm not sure, but raising this significantly may solve the problem:
myisam_max_sort_file_size 16777216000
Suggest 100G, assuming you have that much disk space to spare.

Do SHOW PROCESSLIST; Does it say "Repair with keycache"? Here are some threads, none of which are conclusive enough to satisfy me:
http://forums.mysql.com/read.php?24,382967 (Create Index Slow)
http://forums.mysql.com/read.php?10,379243 (How to avoid Repair with keycache for indexing big table ?)
http://forums.mysql.com/read.php?21,375635 ("Alter table enable keys" randomly using "Repair with keycache")
http://forums.mysql.com/read.php?21,366172 (Repair Will Not Use Filesort)
http://forums.mysql.com/read.php?24,355844 (how to avoid repair by keycache)
http://forums.mysql.com/read.php?21,286031 (Slow Repair Table with Large Unique Keys)
http://forums.mysql.com/read.php?24,277763 (enable keys, force sort, not keycache)
http://forums.mysql.com/read.php?24,251134 (Speed of bulk inserts degrading over time)
http://forums.mysql.com/read.php?21,120068 (indexing speed)
http://forums.mysql.com/read.php?21,114821 (How to avoid 'Repair with keycache')
http://forums.mysql.com/read.php?21,86150 (Avoiding "Repair with keycache")

Minor comments:

Data Length 27G
Max Data Length 5910974G
implies that the myisam_data_pointer_size (6) for MyISAM indexes is at least 1 byte longer than it need to be. 1 byte = 1328408635 bytes per index = 2.5GB

The 'grinding away' will continue until the entire task (adding 2 indexes) is finished. This will still be faster than adding each index separately.

What will the SELECTs be like?