blog.dir directory in wp-content folder required ?

i was reading in the book "PROFESSIONAL WORDPRESS:
DESIGN AND DEVELOPMENT" that "The first step is to create a blogs.dir directory in your /wp-content directory." but i saw no mention of this here >

https://premium.wpmudev.org/manuals/wpmu-manual-2/creating-a-network-to-enable-wordpress-multisite/

here is the exact book on amazon for your perusal :

http://www.amazon.com/gp/product/111844227X/ref=s9_simh_gw_p14_d0_i1?pf_rd_m=ATVPDKIKX0DER&pf_rd_s=center-2&pf_rd_r=1FEYWZ1G958JG46YF8Y1&pf_rd_t=101&pf_rd_p=1688200382&pf_rd_i=507846

Is this necessary ?
If so why /or/ why not ?

Any kind advice on this would be greatly appreciated.

Kind regards,
RC.