Estate Records can be a valuable genealogy source. Ireland had many estates in the 17th, 18th and 19th centuries, in fact they comprised most of the land. Most rural parishes tended to have one big estate, which could amount to most of the land within that parish. Landlords or their agents managed these estates, which typically involved a big house and demesne and many farms let out to tenants. Records kept include diaries, estate maps, farm accounts, leases, licences, letters, rent rolls, tax receipts. I have found 18th and 19th century references to my estate servant ancestors in all these different types of documents, sufficient to form a picture of their lives within a local history of the area. This is great as so little information is available on ordinary folk in those times. Best approach to finding what records are available is to look up Hayes Guide to Manuscript Sources in the Reading Rooms of the National Library and/or its Manuscript Room or in National Archives.
These libraries have detailed indexes on their shelves of exactly what they hold within each estate collection. Major libraries outside Ireland may also have "Hayes" on their shelves, from which you can get clues before you travel.