Hi Supuluka-san,
I found the answer for my question as below.
That is the same as old branch series.
Hence, I think that the behavior as my testing is the bug.
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Partition install is supported on the default media on SRX300, SRX320, 340, and SRX345 devices (internal NAND flash) and not supported on the alternate media (USB storage key).
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[[Example: Installing Junos OS on SRX Series Devices Using the Partition Option]]
http://www.juniper.net/techpubs/en_US/junos15.1x49-d40/topics/example/security-junos-srx-series-device-using-partition-option-installing.html
[[Dual-Root Partitioning Scheme on SRX Series Devices]]
http://www.juniper.net/techpubs/en_US/junos15.1x49-d40/topics/concept/security-dual-root-partitioning-scheme-overview.html
Regards,
GENC