IDE interface and SCSI interface are the most widely used in the storage device. SCSI bus supports I/O queue but storage device with SCSI interface is some expensive, while IDE bus does not support queue by itself but its price is more acceptable. In this paper, we just propose a twin-queue algorithm to benefit from the trade-off of the performance of the SCSI interface and the cheapness of the IDE storage devices. There are two priority queues, one for the host to respond client requests via SCSI bus, the other for the IDE storage devices where the requested data really locate. It is proved that the performance of the device with twin-queue algorithm is much higher than that of the normal IDE optical drive which is not equipped with our firmware using stochastic queue service model.