iSCSI vs NAS Storage

What is the advantage of iSCSI over NAS you ask? Both NAS ans iSCSI are IP based storage, however NAS is file based storage and iSCSI block based. This means that iSCSI can out perform NAS because it only has to write the blocks that have changed and not the entire file. iSCSI also looks like direct attached storage to the server it's connected to so it works better for backups and other types of applications.