mysql database restore takes long time I am in the process of reinstalling a Ubuntu server to rhel6 server. I have a pretty huge database. When I checked the mysql data directory size, it was around 354 GB. However, I dumped the entire database using the mysqldump command. 

After reinstalling the machine, I started to restore the database using the mysql command. I started the restore process 3 days back. When I checked the mysql data directory in this newly installed machine, the size is just 31 GB. I am confused if actually the mysql command is restoring the database. I still see the command getting executed and the process is visibile from the linux top command. Is there something else I can do to speed up the process?
If you're using largely innodb tables increasing the innodb_buffer_pool_size as large as possible (~80-90% system assuming nothing else but mysqld is really consuming ram).  This requires a mysqld restart though

Before the reload you can also set innodb_flush_log_at_trx_commit=2 to speed things up.  This disables flushing to disk every commit (breaking the D in ACID), but should be fine for a restore.  If there's a catastrophic failure during this process you're starting from scratch anyway.  Be sure to set this back to one after the restore.

This can be changed dynamically without a bounce

Ensure innodb_flush_method = O_DIRECT is set in your cnf.  This requires a restart

Is it getting pegged on CPU in top?  If you have a lot of compressed table data that will be inherently slower.  There's not much that can be done about this aside from getting a faster core.  Multi core wouldn't help you here since the load is done serially anyway.

If you're using spinning disks, if possible ensure the .sql source file is being read from a different set of HDDs.  Similarly, during the reload (unless you're trying to let the reload replicate) ensure binary logging and general logging are turned off.

If you're running 5.6 ensure performance schema is not enabled.