It will most definitely show on a background check. However, the question of whether or not it will keep you from gaining employment depends on your employer, not the law.
If you're interested in pursuing an expungement, feel free to contact me for a free consultation. My practice is based in Oakland and I takes cases all over the bay area.
Sadly this felony will be on your record and could effect your employment chances. What you are confusing is misdemeanor personal possession of marijuana is erased from your records after a certain number of years, not a felony.
The above information does not establish an attorney client relationship nor is it meant to provide legal advice.
You have been convicted of a possession for sale of marijuana, which is a straight felony and will definitely affect your employment for the rest of your life. You could pursue a 1203.4 dismissal and eventually a Certificate of Rehabilitation, both of which will help your employment situation, but your employers will be seeing this conviction for the rest of your life. Your crime is a straight felony and cannot be reduced to a misdemeanor as another attorney suggested. You can apply for an early termination of probation. Feel free to contact me if you are interested in doing so. Good luck to you.