Juniper SRX550, Hardware Manual

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CHAPTER 2
Hardware Component Overview
IN THIS CHAPTER
SRX550 Services Gateway Boot Devices and Dual-Root Partitioning Scheme | 12
SRX550 Services Gateway Boot Devices and Dual-Root Partitioning Scheme
By default, the SRX550 Services Gateway boots from the following storage media (in order of priority):
1. Internal CompactFlash card (default; always present)
2. USB storage key (alternate)
NOTE: When you explicitly boot the services gateway using the CLI and the services gateway
has two USBs installed (one in slot 0 and the second in slot 1), if the USB in slot 0 fails, the
booting sequence will not boot from the second USB installed in slot 1. Instead, the device will
boot using the next storage media in its storage media booting priority list, the internal
CompactFlash card.
The dual-root partitions allow the services gateways to remain functional if there is file system corruption
and facilitate easy recovery of the corrupted file system.
The dual-root partitioning scheme keeps the primary and backup Junos OS images in two independently
bootable root partitions. If the primary root partition is corrupted, the system will be able to boot from
the backup Junos OS image located in the other root partition and remain fully functional.
When the services gateway powers up, it tries to boot Junos OS from the default storage media. If the
device fails to boot from the default storage media, it tries to boot from the alternate storage media. With
the dual-root partitioning scheme, the device first tries to boot Junos OS from the primary root partition
and then from the backup root partition on the default storage media. If both primary and backup root
partitions of a media fail to boot, then the device tries to boot Junos OS from the next available type of
storage media. The services gateway remains fully functional even if it boots the Junos OS from the backup
root partition of storage media.
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