A storage device, comprising: a non-volatile memory, NVM, package; and a controller connected to the NVM package through a channel, and configured to control the NVM package, wherein an interface chip is configured to connect the controller to a plurality of internal channels (ICH1, ICH2), wherein the NVM package includes the interface chip, first NVM devices connected to the interface chip through a first internal channel of said internal channels and second NVM devices connected to the interface chip through a second internal channel of said internal channels, the interface chip is configured to, in response to a first read or write operation request received from the controller, select the first internal channel, connect the first internal channel to the channel, and determine, while the selected first internal channel continues to be used for the execution of the first read or write operation, whether retraining is necessary in relation to the second internal channel and transmit a retraining request to the controller when retraining is necessary, wherein the determination whether retraining is necessary comprises transmitting expected data through the second internal channel to a said second NVM devices, receiving through the second internal channel in response to the transmitted expected data, sampling data from the second NVM devices, and comparing the expected data with the sampling data, wherein the interface chip is configured to, upon determining that retraining is necessary, output the retraining request to the controller using a status read that further comprises NVM status read data, wherein the storage device is configured to perform, using the first internal channel, a second read or write operation on said first NVM devices, and to perform a retraining operation using the second internal channel while performing the second read or write operation. a non-volatile memory, NVM, package; and a controller connected to the NVM package through a channel, and configured to control the NVM package, wherein an interface chip is configured to connect the controller to a plurality of internal channels (ICH1, ICH2), wherein the NVM package includes the interface chip, first NVM devices connected to the interface chip through a first internal channel of said internal channels and second NVM devices connected to the interface chip through a second internal channel of said internal channels, the interface chip is configured to, in response to a first read or write operation request received from the controller, select the first internal channel, connect the first internal channel to the channel, and determine, while the selected first internal channel continues to be used for the execution of the first read or write operation, whether retraining is necessary in relation to the second internal channel and transmit a retraining request to the controller when retraining is necessary, wherein the determination whether retraining is necessary comprises transmitting expected data through the second internal channel to a said second NVM devices, receiving through the second internal channel in response to the transmitted expected data, sampling data from the second NVM devices, and comparing the expected data with the sampling data, wherein the interface chip is configured to, upon determining that retraining is necessary, output the retraining request to the controller using a status read that further comprises NVM status read data, wherein the storage device is configured to perform, using the first internal channel, a second read or write operation on said first NVM devices, and to perform a retraining operation using the second internal channel while performing the second read or write operation.