Grabbing SQL Dump of Master DB Without Downtime

I'm curious whether downtime will be necessary to grab a SQL dump of my master database. Right now, I'm in the process of rebuilding my one slave. There is actually only one database from master that is being replicated onto slave. All tables in that database are InnoDB. This is the command I want to run: mysqldump --master-data --single-transaction --hex-blob dbname | gzip > dbname.sql.gz I'm running MySQL 5.1 and here is a redacted version of my my.cnf file: [mysqld] default-storage-engine=InnoDB character-set-server=UTF8 lower_case_table_names=1 transaction_isolation=READ-COMMITTED wait_timeout=86400 interactive_timeout=3600 delayed_insert_timeout=10000 connect_timeout=100000 max_connections=750 max_connect_errors=1000 back_log=50 max_allowed_packet=1G max_heap_table_size=64M tmp_table_size=64M bulk_insert_buffer_size=128M innodb_buffer_pool_size=10000M innodb_data_file_path=ibdata1:256M:autoextend innodb_file_per_table=1 innodb_additional_mem_pool_size=32M innodb_log_file_size=1G innodb_log_buffer_size=8M innodb_flush_method=O_DIRECT innodb_lock_wait_timeout=240 innodb_flush_log_at_trx_commit=2 innodb_open_files=8192 innodb_support_xa=ON thread_cache_size=500 expire_logs_days=2 server-id=1 log_bin=1 binlog_format=MIXED sync_binlog=0 [mysqldump] max_allowed_packet=128M Am I good without downtime or not? I'm concerned about a possible read lock being placed on tables.