b2: reduce copy part size

'Error copying snapshot/app_8b22dc8f-3e15-4314-8108-bcf1908a24df.tar.gz.enc (482405284 bytes): InternalError InternalError: too busy to complete copy - please try again' }

src/storage/s3.js

@@ -255,8 +255,8 @@ function copy(apiConfig, oldFilePath, newFilePath) {
             };
 
             // S3 copyObject has a file size limit of 5GB so if we have larger files, we do a multipart copy
-            // Exoscale takes too long to copy 5GB
-            const largeFileLimit = apiConfig.provider === 'exoscale-sos' ? 1024 * 1024 * 1024 : 5 * 1024 * 1024 * 1024;
+            // Exoscale and B2 take too long to copy 5GB
+            const largeFileLimit = (apiConfig.provider === 'exoscale-sos' || apiConfig.provider === 'backblaze-b2') ? 1024 * 1024 * 1024 : 5 * 1024 * 1024 * 1024;
 
             if (entry.size < largeFileLimit) {
                 events.emit('progress', `Copying ${relativePath || oldFilePath}`);