Since my R8 doesn't have dual card slots, should I just never shoot weddings ever?

[warne59]

I hear it's not safe to risk it, at least not as the primary shooter. If that's true, should I just save up for a body with a dual card slots, like the R6MII for example? What kind of gigs are safe to do with a single card slot?

[rs-eos]

It's always best to have dual card slots for crucial events.  Though it will be more important to have a solid data plan in place.  i.e. how soon after the event is over, will you back up those cards? Do you have redundant storage either locally and/or the cloud?

Having said that, there are some things you can do to ensure things go as well as possible for cameras with just a single slot:

• Always use full-sized cards from reputable brands purchased from reputable companies.  e.g. do not trust places like Amazon which often have counterfeit cards.
• Always fully format the card before the event.  Also though format the card and ensure it can be written to and read from before the event.
• Hire on a second shooter.
• Capture in RAW+JPEG.  This gives you at least some form of immediate backup.  Albeit with different formats of the images.  While a card could indeed still fail, if RAW images become corrupt, at least you'd have a JPEG as a backup.
• Offload images as often as possible.  Either bring a laptop or other device with you where you can sync all files (to include RAW).  Portable drive solutions also exist where you can make copies of the card data.

At the end of the day, things happen, but you want to minimize the impact of that.  Especially for once-in-a-lifetime events for your clients.

[Waddizzle]

Excellent advice from an excellent source.  I would only add do not shoot with the same card all day long, for the entire event.  

There will always be periodic breaks. CHANGE to a freshly formatted card.

[wq9nsc]

Excellent advice from Ricky and I will add a couple more:

1.  Always have a second body and lens with you for any critical event.  Either/both can fail unexpectedly.  Having a second body also allows you to take shots with both using different focal length glass which gives you both separate presentations of the same scenes AND it provides a very robust form of backup.

2.  After you do that low level format in the camera, move the menu setting to a different non-destructive menu choice so an unintended button push or jostling a camera left powered up doesn't result in formatting your card.

Redundant cards aren't a bad idea BUT there are a lot of sources of failure that dual cards don't address (like a camera board failure that writes destructive data to both your cards) or theft of the camera before you have the data in a safe place.

I shoot primarily sports and although I wouldn't want to lose a play it wouldn't be as critical losing part of a wedding ceremony.  I use only Canon 1 series for sports and these all have dual card slots but I never have both written simultaneously.  In nearly 2 decades of use and shooting hundreds of events, I have never had a data/card issue with these bodies.

I spent much of my career working with enterprise risk management; having a card fail is only one of many potential things that can happen resulting in you not capturing/losing images from a critical event.  So don't focus on dual cards to the exclusion of all of the other risks that need to be managed.

Rodger

[Tronhard]

Since your question assumedly indicates that you are pretty new to wedding photography, I would suggest you consider how you will shoot the wedding to get the best results for you and the celebrants' parties and guests.

In that respect, I recommend looking on You Tube for Vanessa Joy, who is a wedding and events specialist.  She has quite a few videos you may find useful on what to shoot and how to do it. You can contact her to ask specific questions too, I believe.
Also, be aware that emotions can run high during a wedding, and there can be a lot of PR efforts required to get people where you need them to be, and to not ruffle any feathers.
One thing to discuss with the bridal party is cell phones. A lot of guests will bring them to the event wanting to get their own shots.  This can be very problematic if you are providing the 'official' images - for example, as the happy couple go down the isle and you line up to get those classical images, it's a killer when guests step out with arms extended to shoot with a phone in front of you.   Quite a few wedding photographers ask the organizers to tell people to NOT take photos and videos of their own at certain parts of the nuptials.
If you are planning to do this on a paying client basis, you will need a contract that clearly lays out what you will provide and in what form, and for what price.   Even if it is as a volunteer, you need to know what they expect and some kind of memorandum may be of use instead.