4 bay nas memory capacity 4 tb number of installed hard drives 2 max hard drives 4 memory capacity per hard drive 2 tb hard drive form factors 25 35 inch hard drive types hdd ssd hard drive mountings screwed removable drive hard drive access front hard drive location horizontal internal interface sata iii target audience business internal file system ext4 external file systems ext3 ext4 ntfs hfs fat raid levels 0 1 5 6 10 jbod synology hy