Moving an ibd file temporarily to free up disk space I want to optimize an InnoDB table but I do not have enough disk space. I have enabled innodb_file_per_table, so each table has *.ibd for each of their partitions. For example:

512MB /var/lib/mysql/ib_logfile0
512MB /var/lib/mysql/ib_logfile1
 70GB /var/lib/mysql/ibdata1
100GB /var/lib/mysql/dbname/table_a.ibd    (*)
100GB /var/lib/mysql/dbname/table_b.ibd    (*)
 12KB /var/lib/mysql/dbname/table_a.frm
 12KB /var/lib/mysql/dbname/table_b.frm
  4KB /var/lib/mysql/dbname/table_a.TRG
  4KB /var/lib/mysql/dbname/table_b.TRG


Is it okay to move table_a.ibd to another disk, optmize table_b, and move table_a.ibd back to its original place? I don't want to lose any data, or break anything.

MySQL server version 5.1.73
It would make more sense to me to take a backup, remove the table instead of moving it, perform your optimize and then restore the table you dropped. This would avoid moving tables around unnecessarily and leaving your database in an incoherent state. You would also want to prevent incoming connections from the outside by putting bind-address = 127.0.0.1 in my.cnf and then restarting mysql. 

Backup your whole database first with mysqldump

mysqldump 
--single-transaction \
--routines \
-u root -p nameofdatabase | gzip -9 &gt; nameofdatabase.gz


--single-transaction is the safest way to backup innodb

--routines backsup stored procedures.

gzip just compresses the backup nicely, you can open it backup with zcat. 

1: Backup the table in question

mysqldump 
--single-transaction \
-u root -p nameofdatabase nameoftable | gzip -9 &gt; nameoftable.gz


2: Make sure the backup you created of the table has your data with zcat

zcat nameoftable.gz | less


Drop the table

mysql&gt; drop table nameoftable;


3: Perform your maintenance with optimize

4: Restore the table

zcat nameoftable.gz | mysql -u root -p nameofdatabase