Comment 3 for bug 1017729

While the UI itself does not clearly state the units of this setting, you can see it in the code in clc/modules/core/src/main/java/edu/ucsb/eucalyptus/cloud/entities/StorageInfo.java:

       @ConfigurableField( description = "Total disk space reserved for volumes", displayName = "Disk space reserved for volumes" )
        @Column( name = "system_storage_volume_size_gb" )
        private Integer maxTotalVolumeSizeInGb;

So the unit is GB, meaning that a value of "6000000" is approximately 6 Petabytes. I am guessing you were specifying this assuming that it was a smaller unit.