diff --git a/Remote.hs b/Remote.hs
index 29097f77d3..5ee75823f5 100644
--- a/Remote.hs
+++ b/Remote.hs
@@ -56,6 +56,7 @@ import Data.Ord
 import Common.Annex
 import Types.Remote
 import qualified Annex
+import Annex.Exception
 import Annex.UUID
 import Logs.UUID
 import Logs.Trust
@@ -312,3 +313,10 @@ isXMPPRemote :: Remote -> Bool
 isXMPPRemote remote = Git.repoIsUrl r && "xmpp::" `isPrefixOf` Git.repoLocation r
   where
 	r = repo remote
+
+hasKey :: Remote -> Key -> Annex (Either String Bool)
+hasKey r k = either (Left  . show) Right
+	<$> tryNonAsyncAnnex (checkPresent r k)
+
+hasKeyCheap :: Remote -> Bool
+hasKeyCheap = checkPresentCheap
diff --git a/Remote/Bup.hs b/Remote/Bup.hs
index 6a04ad5f7f..2e68f30ef7 100644
--- a/Remote/Bup.hs
+++ b/Remote/Bup.hs
@@ -58,8 +58,8 @@ gen r u c gc = do
 		, retrieveKeyFile = retreiveKeyFileDummy
 		, retrieveKeyFileCheap = retrieveCheap buprepo
 		, removeKey = remove buprepo
-		, hasKey = checkPresent r bupr'
-		, hasKeyCheap = bupLocal buprepo
+		, checkPresent = checkKey r bupr'
+		, checkPresentCheap = bupLocal buprepo
 		, whereisKey = Nothing
 		, remoteFsck = Nothing
 		, repairRepo = Nothing
@@ -163,14 +163,13 @@ remove buprepo k = do
  - in a bup repository. One way it to check if the git repository has
  - a branch matching the name (as created by bup split -n).
  -}
-checkPresent :: Git.Repo -> Git.Repo -> Key -> Annex (Either String Bool)
-checkPresent r bupr k
+checkKey :: Git.Repo -> Git.Repo -> Key -> Annex Bool
+checkKey r bupr k
 	| Git.repoIsUrl bupr = do
 		showChecking r
-		ok <- onBupRemote bupr boolSystem "git" params
-		return $ Right ok
-	| otherwise = liftIO $ catchMsgIO $
-		boolSystem "git" $ Git.Command.gitCommandLine params bupr
+		onBupRemote bupr boolSystem "git" params
+	| otherwise = liftIO $ boolSystem "git" $
+		Git.Command.gitCommandLine params bupr
   where
 	params = 
 		[ Params "show-ref --quiet --verify"
diff --git a/Remote/Ddar.hs b/Remote/Ddar.hs
index b4c7ac1e62..1227b52755 100644
--- a/Remote/Ddar.hs
+++ b/Remote/Ddar.hs
@@ -54,8 +54,8 @@ gen r u c gc = do
 		, retrieveKeyFile = retreiveKeyFileDummy
 		, retrieveKeyFileCheap = retrieveCheap
 		, removeKey = remove ddarrepo
-		, hasKey = checkPresent ddarrepo
-		, hasKeyCheap = ddarLocal ddarrepo
+		, checkPresent = checkKey ddarrepo
+		, checkPresentCheap = ddarLocal ddarrepo
 		, whereisKey = Nothing
 		, remoteFsck = Nothing
 		, repairRepo = Nothing
@@ -181,13 +181,14 @@ inDdarManifest ddarrepo k = do
   where
 	k' = key2file k
 
-checkPresent :: DdarRepo -> Key -> Annex (Either String Bool)
-checkPresent ddarrepo key = do
+checkKey :: DdarRepo -> Key -> Annex Bool
+checkKey ddarrepo key = do
 	directoryExists <- ddarDirectoryExists ddarrepo
 	case directoryExists of
-		Left e -> return $ Left e
-		Right True -> inDdarManifest ddarrepo key
-		Right False -> return $ Right False
+		Left e -> error e
+		Right True -> either error return
+			=<< inDdarManifest ddarrepo key
+		Right False -> return False
 
 ddarLocal :: DdarRepo -> Bool
 ddarLocal = notElem ':'
diff --git a/Remote/Directory.hs b/Remote/Directory.hs
index 9b3c156959..0a2532aa5b 100644
--- a/Remote/Directory.hs
+++ b/Remote/Directory.hs
@@ -52,8 +52,8 @@ gen r u c gc = do
 			retrieveKeyFile = retreiveKeyFileDummy,
 			retrieveKeyFileCheap = retrieveCheap dir chunkconfig,
 			removeKey = remove dir,
-			hasKey = checkPresent dir chunkconfig,
-			hasKeyCheap = True,
+			checkPresent = checkKey dir chunkconfig,
+			checkPresentCheap = True,
 			whereisKey = Nothing,
 			remoteFsck = Nothing,
 			repairRepo = Nothing,
@@ -189,13 +189,10 @@ removeDirGeneric topdir dir = do
 		then return ok
 		else doesDirectoryExist topdir <&&> (not <$> doesDirectoryExist dir)
 
-checkPresent :: FilePath -> ChunkConfig -> Key -> Annex (Either String Bool)
-checkPresent d (LegacyChunks _) k = Legacy.checkPresent d locations k
-checkPresent d _ k = liftIO $ do
-	v <- catchMsgIO $ anyM doesFileExist (locations d k)
-	case v of
-		Right False -> ifM (doesDirectoryExist d)
-			( return v
-			, return $ Left $ "directory " ++ d ++ " is not accessible"
-			)
-		_ -> return v
+checkKey :: FilePath -> ChunkConfig -> Key -> Annex Bool
+checkKey d (LegacyChunks _) k = Legacy.checkKey d locations k
+checkKey d _ k = liftIO $
+	ifM (anyM doesFileExist (locations d k))
+		( return True
+		, error $ "directory " ++ d ++ " is not accessible"
+		)
diff --git a/Remote/Directory/LegacyChunked.hs b/Remote/Directory/LegacyChunked.hs
index 1be885db21..b2248c5f66 100644
--- a/Remote/Directory/LegacyChunked.hs
+++ b/Remote/Directory/LegacyChunked.hs
@@ -103,8 +103,7 @@ retrieve locations d basek a = do
 		liftIO $ nukeFile tmp
 		sink b
 
-checkPresent :: FilePath -> (FilePath -> Key -> [FilePath]) -> Key -> Annex (Either String Bool)
-checkPresent d locations k = liftIO $ catchMsgIO $
-	withStoredFiles d locations k $
-		-- withStoredFiles checked that it exists
-		const $ return True
+checkKey :: FilePath -> (FilePath -> Key -> [FilePath]) -> Key -> Annex Bool
+checkKey d locations k = liftIO $ withStoredFiles d locations k $
+	-- withStoredFiles checked that it exists
+	const $ return True
diff --git a/Remote/External.hs b/Remote/External.hs
index c00093402f..ffae94ec99 100644
--- a/Remote/External.hs
+++ b/Remote/External.hs
@@ -53,8 +53,8 @@ gen r u c gc = do
 			retrieveKeyFile = retreiveKeyFileDummy,
 			retrieveKeyFileCheap = \_ _ -> return False,
 			removeKey = remove external,
-			hasKey = checkPresent external,
-			hasKeyCheap = False,
+			checkPresent = checkKey external,
+			checkPresentCheap = False,
 			whereisKey = Nothing,
 			remoteFsck = Nothing,
 			repairRepo = Nothing,
@@ -121,8 +121,8 @@ remove external k = safely $
 					return False
 			_ -> Nothing
 
-checkPresent :: External -> Key -> Annex (Either String Bool)
-checkPresent external k = either (Left . show) id <$> tryAnnex go
+checkKey :: External -> Key -> Annex Bool
+checkKey external k = either error id <$> go
   where
 	go = handleRequest external (CHECKPRESENT k) Nothing $ \resp ->
 		case resp of
diff --git a/Remote/GCrypt.hs b/Remote/GCrypt.hs
index d969e02f8a..f971ff754f 100644
--- a/Remote/GCrypt.hs
+++ b/Remote/GCrypt.hs
@@ -46,7 +46,6 @@ import Utility.Tmp
 import Logs.Remote
 import Logs.Transfer
 import Utility.Gpg
-import Utility.FileMode
 
 remote :: RemoteType
 remote = RemoteType {
@@ -109,8 +108,8 @@ gen' r u c gc = do
 		, retrieveKeyFile = retreiveKeyFileDummy
 		, retrieveKeyFileCheap = \_ _ -> return False
 		, removeKey = remove this rsyncopts
-		, hasKey = checkPresent this rsyncopts
-		, hasKeyCheap = repoCheap r
+		, checkPresent = checkKey this rsyncopts
+		, checkPresentCheap = repoCheap r
 		, whereisKey = Nothing
 		, remoteFsck = Nothing
 		, repairRepo = Nothing
@@ -342,16 +341,15 @@ remove r rsyncopts k
 	removersync = Remote.Rsync.remove rsyncopts k
 	removeshell = Ssh.dropKey (repo r) k
 
-checkPresent :: Remote -> Remote.Rsync.RsyncOpts -> Key -> Annex (Either String Bool)
-checkPresent r rsyncopts k
+checkKey :: Remote -> Remote.Rsync.RsyncOpts -> Key -> Annex Bool
+checkKey r rsyncopts k
 	| not $ Git.repoIsUrl (repo r) =
 		guardUsable (repo r) (cantCheck $ repo r) $
-			liftIO $ catchDefaultIO (cantCheck $ repo r) $
-				Right <$> doesFileExist (gCryptLocation r k)
+			liftIO $ doesFileExist (gCryptLocation r k)
 	| Git.repoIsSsh (repo r) = shellOrRsync r checkshell checkrsync
 	| otherwise = unsupportedUrl
   where
-  	checkrsync = Remote.Rsync.checkPresent (repo r) rsyncopts k
+  	checkrsync = Remote.Rsync.checkKey (repo r) rsyncopts k
 	checkshell = Ssh.inAnnex (repo r) k
 
 {- Annexed objects are hashed using lower-case directories for max
diff --git a/Remote/Git.hs b/Remote/Git.hs
index c35f9f32af..da5ca4c4a5 100644
--- a/Remote/Git.hs
+++ b/Remote/Git.hs
@@ -141,8 +141,8 @@ gen r u c gc
 			, retrieveKeyFile = copyFromRemote new
 			, retrieveKeyFileCheap = copyFromRemoteCheap new
 			, removeKey = dropKey new
-			, hasKey = inAnnex new
-			, hasKeyCheap = repoCheap r
+			, checkPresent = inAnnex new
+			, checkPresentCheap = repoCheap r
 			, whereisKey = Nothing
 			, remoteFsck = if Git.repoIsUrl r
 				then Nothing
@@ -284,11 +284,8 @@ tryGitConfigRead r
 			void $ tryAnnex $ ensureInitialized
 			Annex.getState Annex.repo
 
-{- Checks if a given remote has the content for a key inAnnex.
- - If the remote cannot be accessed, or if it cannot determine
- - whether it has the content, returns a Left error message.
- -}
-inAnnex :: Remote -> Key -> Annex (Either String Bool)
+{- Checks if a given remote has the content for a key in its annex. -}
+inAnnex :: Remote -> Key -> Annex Bool
 inAnnex rmt key
 	| Git.repoIsHttp r = checkhttp
 	| Git.repoIsUrl r = checkremote
@@ -298,17 +295,13 @@ inAnnex rmt key
 	checkhttp = do
 		showChecking r
 		ifM (Url.withUrlOptions $ \uo -> anyM (\u -> Url.checkBoth u (keySize key) uo) (keyUrls rmt key))
-			( return $ Right True
-			, return $ Left "not found"
+			( return True
+			, error "not found"
 			)
 	checkremote = Ssh.inAnnex r key
-	checklocal = guardUsable r (cantCheck r) $ dispatch <$> check
-	  where
-		check = either (Left . show) Right 
-			<$> tryAnnex (onLocal rmt $ Annex.Content.inAnnexSafe key)
-		dispatch (Left e) = Left e
-		dispatch (Right (Just b)) = Right b
-		dispatch (Right Nothing) = cantCheck r
+	checklocal = guardUsable r (cantCheck r) $
+		fromMaybe (cantCheck r)
+			<$> onLocal rmt (Annex.Content.inAnnexSafe key)
 
 keyUrls :: Remote -> Key -> [String]
 keyUrls r key = map tourl locs'
diff --git a/Remote/Glacier.hs b/Remote/Glacier.hs
index c5bfefa641..2ade37011e 100644
--- a/Remote/Glacier.hs
+++ b/Remote/Glacier.hs
@@ -52,8 +52,8 @@ gen r u c gc = new <$> remoteCost gc veryExpensiveRemoteCost
 			retrieveKeyFile = retreiveKeyFileDummy,
 			retrieveKeyFileCheap = retrieveCheap this,
 			removeKey = remove this,
-			hasKey = checkPresent this,
-			hasKeyCheap = False,
+			checkPresent = checkKey this,
+			checkPresentCheap = False,
 			whereisKey = Nothing,
 			remoteFsck = Nothing,
 			repairRepo = Nothing,
@@ -164,25 +164,21 @@ remove r k = glacierAction r
 	, Param $ archive r k
 	]
 
-checkPresent :: Remote -> Key -> Annex (Either String Bool)
-checkPresent r k = do
+checkKey :: Remote -> Key -> Annex Bool
+checkKey r k = do
 	showAction $ "checking " ++ name r
 	go =<< glacierEnv (config r) (uuid r)
   where
-	go Nothing = return $ Left "cannot check glacier"
+	go Nothing = error "cannot check glacier"
 	go (Just e) = do
 		{- glacier checkpresent outputs the archive name to stdout if
 		 - it's present. -}
-		v <- liftIO $ catchMsgIO $ 
-			readProcessEnv "glacier" (toCommand params) (Just e)
-		case v of
-			Right s -> do
-				let probablypresent = key2file k `elem` lines s
-				if probablypresent
-					then ifM (Annex.getFlag "trustglacier")
-						( return $ Right True, untrusted )
-					else return $ Right False
-			Left err -> return $ Left err
+		s <- liftIO $ readProcessEnv "glacier" (toCommand params) (Just e)
+		let probablypresent = key2file k `elem` lines s
+		if probablypresent
+			then ifM (Annex.getFlag "trustglacier")
+				( return True, error untrusted )
+			else return False
 
 	params = glacierParams (config r)
 		[ Param "archive"
@@ -192,7 +188,7 @@ checkPresent r k = do
 		, Param $ archive r k
 		]
 
-	untrusted = return $ Left $ unlines
+	untrusted = unlines
 			[ "Glacier's inventory says it has a copy."
 			, "However, the inventory could be out of date, if it was recently removed."
 			, "(Use --trust-glacier if you're sure it's still in Glacier.)"
diff --git a/Remote/Helper/Chunked.hs b/Remote/Helper/Chunked.hs
index 7ad790cb16..953c533b66 100644
--- a/Remote/Helper/Chunked.hs
+++ b/Remote/Helper/Chunked.hs
@@ -12,7 +12,7 @@ module Remote.Helper.Chunked (
 	storeChunks,
 	removeChunks,
 	retrieveChunks,
-	hasKeyChunks,
+	checkPresentChunks,
 ) where
 
 import Common.Annex
@@ -94,8 +94,8 @@ storeChunks
 	-> Key
 	-> FilePath
 	-> MeterUpdate
-	-> (Key -> ContentSource -> MeterUpdate -> Annex Bool)
-	-> (Key -> Annex (Either String Bool))
+	-> Storer
+	-> CheckPresent
 	-> Annex Bool
 storeChunks u chunkconfig k f p storer checker = 
 	case chunkconfig of
@@ -158,7 +158,7 @@ storeChunks u chunkconfig k f p storer checker =
 seekResume
 	:: Handle
 	-> ChunkKeyStream
-	-> (Key -> Annex (Either String Bool))
+	-> CheckPresent
 	-> Annex (ChunkKeyStream, BytesProcessed)
 seekResume h chunkkeys checker = do
 	sz <- liftIO (hFileSize h)
@@ -172,7 +172,7 @@ seekResume h chunkkeys checker = do
 			liftIO $ hSeek h AbsoluteSeek sz
 			return (cks, toBytesProcessed sz)
 		| otherwise = do
-			v <- checker k
+			v <- tryNonAsyncAnnex (checker k)
 			case v of
 				Right True ->
 					check pos' cks' sz
@@ -331,43 +331,48 @@ setupResume ls currsize = map dropunneeded ls
 {- Checks if a key is present in a remote. This requires any one
  - of the lists of options returned by chunkKeys to all check out
  - as being present using the checker action.
+ -
+ - Throws an exception if the remote is not accessible.
  -}
-hasKeyChunks
-	:: (Key -> Annex (Either String Bool))
+checkPresentChunks
+	:: CheckPresent
 	-> UUID
 	-> ChunkConfig
 	-> EncKey
 	-> Key
-	-> Annex (Either String Bool)
-hasKeyChunks checker u chunkconfig encryptor basek
-	| noChunks chunkconfig =
+	-> Annex Bool
+checkPresentChunks checker u chunkconfig encryptor basek
+	| noChunks chunkconfig = do
 		-- Optimisation: Try the unchunked key first, to avoid
 		-- looking in the git-annex branch for chunk counts
 		-- that are likely not there.
-		ifM ((Right True ==) <$> checker (encryptor basek))
-			( return (Right True)
-			, checklists Nothing =<< chunkKeysOnly u basek
-			)
+		v <- check basek
+		case v of
+			Right True -> return True
+			_ -> checklists Nothing =<< chunkKeysOnly u basek
 	| otherwise = checklists Nothing =<< chunkKeys u chunkconfig basek
   where
-	checklists Nothing [] = return (Right False)
-	checklists (Just deferrederror) [] = return (Left deferrederror)
+	checklists Nothing [] = return False
+	checklists (Just deferrederror) [] = error deferrederror
 	checklists d (l:ls)
 		| not (null l) = do
 			v <- checkchunks l
 			case v of
 				Left e -> checklists (Just e) ls
-				Right True -> return (Right True)
+				Right True -> return True
 				Right False -> checklists Nothing ls
 		| otherwise = checklists d ls
 	
 	checkchunks :: [Key] -> Annex (Either String Bool)
 	checkchunks [] = return (Right True)
 	checkchunks (k:ks) = do
-		v <- checker (encryptor k)
-		if v == Right True
-			then checkchunks ks
-			else return v
+		v <- check k
+		case v of
+			Right True -> checkchunks ks
+			Right False -> return $ Right False
+			Left e -> return $ Left $ show e
+
+	check = tryNonAsyncAnnex . checker . encryptor
 
 {- A key can be stored in a remote unchunked, or as a list of chunked keys.
  - This can be the case whether or not the remote is currently configured
diff --git a/Remote/Helper/Encryptable.hs b/Remote/Helper/Encryptable.hs
index 65a3ba284d..c364a69e76 100644
--- a/Remote/Helper/Encryptable.hs
+++ b/Remote/Helper/Encryptable.hs
@@ -91,9 +91,9 @@ encryptableRemote c storeKeyEncrypted retrieveKeyFileEncrypted r = r
 	, removeKey = \k -> cip k >>= maybe
 		(removeKey r k)
 		(\(_, enckey) -> removeKey r enckey)
-	, hasKey = \k -> cip k >>= maybe
-		(hasKey r k)
-		(\(_, enckey) -> hasKey r enckey)
+	, checkPresent = \k -> cip k >>= maybe
+		(checkPresent r k)
+		(\(_, enckey) -> checkPresent r enckey)
 	, cost = maybe
 		(cost r)
 		(const $ cost r + encryptedRemoteCostAdj)
diff --git a/Remote/Helper/Hooks.hs b/Remote/Helper/Hooks.hs
index c3ff970c62..907400bd1c 100644
--- a/Remote/Helper/Hooks.hs
+++ b/Remote/Helper/Hooks.hs
@@ -39,7 +39,7 @@ addHooks' r starthook stophook = r'
 		, retrieveKeyFile = \k f d p -> wrapper $ retrieveKeyFile r k f d p
 		, retrieveKeyFileCheap = \k f -> wrapper $ retrieveKeyFileCheap r k f
 		, removeKey = wrapper . removeKey r
-		, hasKey = wrapper . hasKey r
+		, checkPresent = wrapper . checkPresent r
 		}
 	  where
 		wrapper = runHooks r' starthook stophook
diff --git a/Remote/Helper/Messages.hs b/Remote/Helper/Messages.hs
index c4b1966dc8..3088a9ab2b 100644
--- a/Remote/Helper/Messages.hs
+++ b/Remote/Helper/Messages.hs
@@ -13,5 +13,5 @@ import qualified Git
 showChecking :: Git.Repo -> Annex ()
 showChecking r = showAction $ "checking " ++ Git.repoDescribe r
 
-cantCheck :: Git.Repo -> Either String Bool
-cantCheck r = Left $ "unable to check " ++ Git.repoDescribe r
+cantCheck :: Git.Repo -> a
+cantCheck r = error $ "unable to check " ++ Git.repoDescribe r
diff --git a/Remote/Helper/Special.hs b/Remote/Helper/Special.hs
index 2bcb7d530d..3c19f25eb9 100644
--- a/Remote/Helper/Special.hs
+++ b/Remote/Helper/Special.hs
@@ -148,7 +148,7 @@ specialRemote' cfg c preparestorer prepareretriever baser = encr
 			(retrieveKeyFileCheap baser k d)
 			(\_ -> return False)
 		, removeKey = \k -> cip >>= removeKeyGen k
-		, hasKey = \k -> cip >>= hasKeyGen k
+		, checkPresent = \k -> cip >>= checkPresentGen k
 		, cost = maybe
 			(cost baser)
 			(const $ cost baser + encryptedRemoteCostAdj)
@@ -167,7 +167,7 @@ specialRemote' cfg c preparestorer prepareretriever baser = encr
 			displayprogress p k $ \p' ->
 				storeChunks (uuid baser) chunkconfig k src p'
 					(storechunk enc storer)
-					(hasKey baser)
+					(checkPresent baser)
 		go Nothing = return False
 		rollback = void $ removeKey encr k
 
@@ -193,10 +193,10 @@ specialRemote' cfg c preparestorer prepareretriever baser = encr
 		enck = maybe id snd enc
 		remover = removeKey baser
 
-	hasKeyGen k enc = hasKeyChunks checker (uuid baser) chunkconfig enck k
+	checkPresentGen k enc = checkPresentChunks checker (uuid baser) chunkconfig enck k
 	  where
 		enck = maybe id snd enc
-		checker = hasKey baser
+		checker = checkPresent baser
 
 	chunkconfig = chunkConfig cfg
 
diff --git a/Remote/Helper/Ssh.hs b/Remote/Helper/Ssh.hs
index 05a98865ff..42d77ea592 100644
--- a/Remote/Helper/Ssh.hs
+++ b/Remote/Helper/Ssh.hs
@@ -81,14 +81,14 @@ onRemote r (with, errorval) command params fields = do
 		Nothing -> return errorval
 
 {- Checks if a remote contains a key. -}
-inAnnex :: Git.Repo -> Key -> Annex (Either String Bool)
+inAnnex :: Git.Repo -> Key -> Annex Bool
 inAnnex r k = do
 	showChecking r
 	onRemote r (check, cantCheck r) "inannex" [Param $ key2file k] []
   where
 	check c p = dispatch <$> safeSystem c p
-	dispatch ExitSuccess = Right True
-	dispatch (ExitFailure 1) = Right False
+	dispatch ExitSuccess = True
+	dispatch (ExitFailure 1) = False
 	dispatch _ = cantCheck r
 
 {- Removes a key from a remote. -}
diff --git a/Remote/Hook.hs b/Remote/Hook.hs
index efbd9f8ba4..037f71ced4 100644
--- a/Remote/Hook.hs
+++ b/Remote/Hook.hs
@@ -45,8 +45,8 @@ gen r u c gc = do
 			retrieveKeyFile = retreiveKeyFileDummy,
 			retrieveKeyFileCheap = retrieveCheap hooktype,
 			removeKey = remove hooktype,
-			hasKey = checkPresent r hooktype,
-			hasKeyCheap = False,
+			checkPresent = checkKey r hooktype,
+			checkPresentCheap = False,
 			whereisKey = Nothing,
 			remoteFsck = Nothing,
 			repairRepo = Nothing,
@@ -128,11 +128,11 @@ retrieveCheap _ _ _ = return False
 remove :: HookName -> Key -> Annex Bool
 remove h k = runHook h "remove" k Nothing $ return True
 
-checkPresent :: Git.Repo -> HookName -> Key -> Annex (Either String Bool)
-checkPresent r h k = do
+checkKey :: Git.Repo -> HookName -> Key -> Annex Bool
+checkKey r h k = do
 	showAction $ "checking " ++ Git.repoDescribe r
 	v <- lookupHook h action
-	liftIO $ catchMsgIO $ check v
+	liftIO $ check v
   where
   	action = "checkpresent"
 	findkey s = key2file k `elem` lines s
diff --git a/Remote/Rsync.hs b/Remote/Rsync.hs
index 421c451bdd..91070fe846 100644
--- a/Remote/Rsync.hs
+++ b/Remote/Rsync.hs
@@ -12,7 +12,7 @@ module Remote.Rsync (
 	store,
 	retrieve,
 	remove,
-	checkPresent,
+	checkKey,
 	withRsyncScratchDir,
 	genRsyncOpts,
 	RsyncOpts
@@ -66,8 +66,8 @@ gen r u c gc = do
 			, retrieveKeyFile = retreiveKeyFileDummy
 			, retrieveKeyFileCheap = retrieveCheap o
 			, removeKey = remove o
-			, hasKey = checkPresent r o
-			, hasKeyCheap = False
+			, checkPresent = checkKey r o
+			, checkPresentCheap = False
 			, whereisKey = Nothing
 			, remoteFsck = Nothing
 			, repairRepo = Nothing
@@ -214,14 +214,12 @@ remove o k = do
 		, dir </> keyFile k </> "***"
 		]
 
-checkPresent :: Git.Repo -> RsyncOpts -> Key -> Annex (Either String Bool)
-checkPresent r o k = do
+checkKey :: Git.Repo -> RsyncOpts -> Key -> Annex Bool
+checkKey r o k = do
 	showAction $ "checking " ++ Git.repoDescribe r
 	-- note: Does not currently differentiate between rsync failing
 	-- to connect, and the file not being present.
-	Right <$> check
-  where
-	check = untilTrue (rsyncUrls o k) $ \u -> 
+	untilTrue (rsyncUrls o k) $ \u -> 
 		liftIO $ catchBoolIO $ do
 			withQuietOutput createProcessSuccess $
 				proc "rsync" $ toCommand $
diff --git a/Remote/S3.hs b/Remote/S3.hs
index 8603757eb6..4c1f1ecfda 100644
--- a/Remote/S3.hs
+++ b/Remote/S3.hs
@@ -57,8 +57,8 @@ gen r u c gc = new <$> remoteCost gc expensiveRemoteCost
 			retrieveKeyFile = retreiveKeyFileDummy,
 			retrieveKeyFileCheap = retrieveCheap this,
 			removeKey = remove this c,
-			hasKey = checkPresent this,
-			hasKeyCheap = False,
+			checkPresent = checkKey this,
+			checkPresentCheap = False,
 			whereisKey = Nothing,
 			remoteFsck = Nothing,
 			repairRepo = Nothing,
@@ -167,16 +167,16 @@ remove' :: Remote -> Key -> Annex Bool
 remove' r k = s3Action r False $ \(conn, bucket) ->
 	s3Bool =<< liftIO (deleteObject conn $ bucketKey r bucket k)
 
-checkPresent :: Remote -> Key -> Annex (Either String Bool)
-checkPresent r k = s3Action r noconn $ \(conn, bucket) -> do
+checkKey :: Remote -> Key -> Annex Bool
+checkKey r k = s3Action r noconn $ \(conn, bucket) -> do
 	showAction $ "checking " ++ name r
 	res <- liftIO $ getObjectInfo conn $ bucketKey r bucket k
 	case res of
-		Right _ -> return $ Right True
-		Left (AWSError _ _) -> return $ Right False
-		Left e -> return $ Left (s3Error e)
+		Right _ -> return True
+		Left (AWSError _ _) -> return False
+		Left e -> s3Error e
   where
-	noconn = Left $ error "S3 not configured"
+	noconn = error "S3 not configured"
 			
 s3Warning :: ReqError -> Annex Bool
 s3Warning e = do
diff --git a/Remote/Tahoe.hs b/Remote/Tahoe.hs
index d265d7ac12..6e52c09810 100644
--- a/Remote/Tahoe.hs
+++ b/Remote/Tahoe.hs
@@ -72,8 +72,8 @@ gen r u c gc = do
 		retrieveKeyFile = retrieve u hdl,
 		retrieveKeyFileCheap = \_ _ -> return False,
 		removeKey = remove,
-		hasKey = checkPresent u hdl,
-		hasKeyCheap = False,
+		checkPresent = checkKey u hdl,
+		checkPresentCheap = False,
 		whereisKey = Nothing,
 		remoteFsck = Nothing,
 		repairRepo = Nothing,
@@ -123,14 +123,16 @@ remove _k = do
 	warning "content cannot be removed from tahoe remote"
 	return False
 
-checkPresent :: UUID -> TahoeHandle -> Key -> Annex (Either String Bool)
-checkPresent u hdl k = go =<< getCapability u k
+checkKey :: UUID -> TahoeHandle -> Key -> Annex Bool
+checkKey u hdl k = go =<< getCapability u k
   where
-	go Nothing = return (Right False)
-	go (Just cap) = liftIO $ parseCheck <$> readTahoe hdl "check"
-		[ Param "--raw"
-		, Param cap
-		]
+	go Nothing = return False
+	go (Just cap) = liftIO $ do
+		v <- parseCheck <$> readTahoe hdl "check"
+			[ Param "--raw"
+			, Param cap
+			]
+		either error return v
 
 defaultTahoeConfigDir :: UUID -> IO TahoeConfigDir
 defaultTahoeConfigDir u = do
diff --git a/Remote/Web.hs b/Remote/Web.hs
index ddd1fc1ccd..7bdd8d1854 100644
--- a/Remote/Web.hs
+++ b/Remote/Web.hs
@@ -50,8 +50,8 @@ gen r _ c gc =
 		retrieveKeyFile = downloadKey,
 		retrieveKeyFileCheap = downloadKeyCheap,
 		removeKey = dropKey,
-		hasKey = checkKey,
-		hasKeyCheap = False,
+		checkPresent = checkKey,
+		checkPresentCheap = False,
 		whereisKey = Just getUrls,
 		remoteFsck = Nothing,
 		repairRepo = Nothing,
@@ -98,12 +98,12 @@ dropKey k = do
 	mapM_ (setUrlMissing k) =<< getUrls k
 	return True
 
-checkKey :: Key -> Annex (Either String Bool)
+checkKey :: Key -> Annex Bool
 checkKey key = do
 	us <- getUrls key
 	if null us
-		then return $ Right False
-		else return =<< checkKey' key us
+		then return False
+		else either error return =<< checkKey' key us
 checkKey' :: Key -> [URLString] -> Annex (Either String Bool)
 checkKey' key us = firsthit us (Right False) $ \u -> do
 	let (u', downloader) = getDownloader u
diff --git a/Remote/WebDAV.hs b/Remote/WebDAV.hs
index 0bdd383602..f0bcac10ea 100644
--- a/Remote/WebDAV.hs
+++ b/Remote/WebDAV.hs
@@ -63,8 +63,8 @@ gen r u c gc = new <$> remoteCost gc expensiveRemoteCost
 			retrieveKeyFile = retrieve this,
 			retrieveKeyFileCheap = retrieveCheap this,
 			removeKey = remove this,
-			hasKey = checkPresent this,
-			hasKeyCheap = False,
+			checkPresent = checkKey this,
+			checkPresentCheap = False,
 			whereisKey = Nothing,
 			remoteFsck = Nothing,
 			repairRepo = Nothing,
@@ -170,10 +170,10 @@ remove r k = davAction r False $ \(baseurl, user, pass) -> liftIO $ do
 	let url = davLocation baseurl k
 	isJust . eitherToMaybe <$> tryNonAsync (deleteDAV url user pass)
 
-checkPresent :: Remote -> Key -> Annex (Either String Bool)
-checkPresent r k = davAction r noconn go
+checkKey :: Remote -> Key -> Annex Bool
+checkKey r k = davAction r noconn (either error id <$$> go)
   where
-	noconn = Left $ error $ name r ++ " not configured"
+	noconn = error $ name r ++ " not configured"
 
 	go (baseurl, user, pass) = do
 		showAction $ "checking " ++ name r
diff --git a/Types/Remote.hs b/Types/Remote.hs
index 805b984740..b657cfcdc5 100644
--- a/Types/Remote.hs
+++ b/Types/Remote.hs
@@ -68,12 +68,12 @@ data RemoteA a = Remote {
 	retrieveKeyFileCheap :: Key -> FilePath -> a Bool,
 	-- removes a key's contents (succeeds if the contents are not present)
 	removeKey :: Key -> a Bool,
-	-- Checks if a key is present in the remote; if the remote
-	-- cannot be accessed returns a Left error message.
-	hasKey :: Key -> a (Either String Bool),
-	-- Some remotes can check hasKey without an expensive network
+	-- Checks if a key is present in the remote.
+	-- Throws an exception if the remote cannot be accessed.
+	checkPresent :: Key -> a Bool,
+	-- Some remotes can checkPresent without an expensive network
 	-- operation.
-	hasKeyCheap :: Bool,
+	checkPresentCheap :: Bool,
 	-- Some remotes can provide additional details for whereis.
 	whereisKey :: Maybe (Key -> a [String]),
 	-- Some remotes can run a fsck operation on the remote,
diff --git a/Types/StoreRetrieve.hs b/Types/StoreRetrieve.hs
index 9fc0634c4e..a21fa7866c 100644
--- a/Types/StoreRetrieve.hs
+++ b/Types/StoreRetrieve.hs
@@ -33,3 +33,11 @@ type Storer = Key -> ContentSource -> MeterUpdate -> Annex Bool
 -- callback, which will fully consume the content before returning.
 -- Throws exception if key is not present, or remote is not accessible.
 type Retriever = Key -> MeterUpdate -> (ContentSource -> Annex Bool) -> Annex Bool
+
+-- Action that removes a Key's content from a remote.
+-- Succeeds if key is already not present; never throws exceptions.
+type Remover = Key -> Annex Bool
+
+-- Checks if a Key's content is present on a remote.
+-- Throws an exception if the remote is not accessible.
+type CheckPresent = Key -> Annex Bool
diff --git a/doc/design/assistant/chunks.mdwn b/doc/design/assistant/chunks.mdwn
index a9709a778d..0aa389899a 100644
--- a/doc/design/assistant/chunks.mdwn
+++ b/doc/design/assistant/chunks.mdwn
@@ -91,7 +91,7 @@ cannot tell when we've gotten the last chunk. (Also, we cannot strip
 padding.) Note that `addurl` sometimes generates keys w/o size info
 (particularly, it does so by design when using quvi).
 
-Problem: Also, this makes `hasKey` hard to implement: How can it know if
+Problem: Also, this makes `checkPresent` hard to implement: How can it know if
 all the chunks are present, if the key size is not known?
 
 Problem: Also, this makes it difficult to download encrypted keys, because
@@ -111,7 +111,7 @@ So, SHA256-1048576-c1--xxxxxxx for the first chunk of 1 megabyte.
 Before any chunks are stored, write a chunkcount file, eg
 SHA256-s12345-c0--xxxxxxx. Note that this key is the same as the original
 object's key, except with chunk number set to 0. This file contains both
-the number of chunks, and also the chunk size used. `hasKey` downloads this
+the number of chunks, and also the chunk size used. `checkPresent` downloads this
 file, and then verifies that each chunk is present, looking for keys with
 the expected chunk numbers and chunk size.
 
@@ -126,7 +126,7 @@ Note: This design lets an attacker with logs tell the (appoximate) size of
 objects, by finding the small files that contain a chunk count, and
 correlating when that is written/read and when other files are
 written/read. That could be solved by padding the chunkcount key up to the
-size of the rest of the keys, but that's very innefficient; `hasKey` is not
+size of the rest of the keys, but that's very innefficient; `checkPresent` is not
 designed to need to download large files.
 
 # design 3
@@ -139,7 +139,7 @@ This seems difficult; attacker could probably tell where the first encrypted
 part stops and the next encrypted part starts by looking for gpg headers,
 and so tell which files are the first chunks.
 
-Also, `hasKey` would need to download some or all of the first file.
+Also, `checkPresent` would need to download some or all of the first file.
 If all, that's a lot more expensive. If only some is downloaded, an
 attacker can guess that the file that was partially downloaded is the
 first chunk in a series, and wait for a time when it's fully downloaded to
@@ -163,7 +163,7 @@ The location log does not record locations of individual chunk keys
 (too space-inneficient). Instead, look at a chunk log in the
 git-annex branch to get the chunk count and size for a key.
 
-`hasKey` would check if any of the logged sets of chunks is 
+`checkPresent` would check if any of the logged sets of chunks is 
 present on the remote. It would also check if the non-chunked key is
 present, as a fallback.
 
@@ -225,7 +225,7 @@ Reasons:
 
 Note that this means that the chunks won't exactly match the configured
 chunk size. gpg does compression, which might make them a
-lot smaller. Or gpg overhead could make them slightly larger. So `hasKey`
+lot smaller. Or gpg overhead could make them slightly larger. So `checkPresent`
 cannot check exact file sizes.
 
 If padding is enabled, gpg compression should be disabled, to not leak
@@ -250,10 +250,10 @@ and skip forward to the next needed chunk. Easy.
 Uploads: Check if the 1st chunk is present. If so, check the second chunk,
 etc. Once the first missing chunk is found, start uploading from there.
 
-That adds one extra hasKey call per upload. Probably a win in most cases.
+That adds one extra checkPresent call per upload. Probably a win in most cases.
 Can be improved by making special remotes open a persistent
 connection that is used for transferring all chunks, as well as for
-checking hasKey.
+checking checkPresent.
 
 Note that this is safe to do only as long as the Key being transferred
 cannot possibly have 2 different contents in different repos. Notably not