Russia had the largest cavalry establishment of all countries in 1914. Cavalry divisions were formed of 2 brigades, the first grouping a dragoon and a lancer regiment, the second a hussar and a cossack regiment. The eastern front saw much more cavalry action than in the west, even cavalry vs cavalry in 1914 Galicia. As late as 1916 there were succesful actions of russian cavalry against advancing infantry.
Some cossack squadrons (sotnia) were alloted to infantry divisions for use as escorts, messengers, local security troops...
Some 50 batteries of Cossack horse artillery were rasied, mainly from Don.
These cossacks will be good for white cavalry, as the Whites had large cossack armies fighting on their side. They can be a proper adversary for Orion's Red Cavalry, that has no place in WW I with their specific headdress.