- The NetWare NOS has built-in system reliability features that safeguard
it against network hardware failure.
- Because these fault tolerance features are built into the operating
system, NetWare delivers fault tolerance without sacrificing performance.
Read-after-Write and Hot Fix:
- Two of NetWare's most basic reliability features are read-after-write
verification and Hot Fix.
- Every time data is written to the network disk, NetWare automatically
performs read-after-write verification, which guarantees that data is readable
at the time it is written.
- NetWare's Hot Fix feature finds faulty areas of the disk, lists them
in a "Bad Block" table, and then relocates data to a usable area--without
affecting normal network operation.
- NetWare's disk-mirroring feature protects your system against data
loss caused by defective hard disks.
- The NetWare NOS duplicates the entire physical volume on a second
hard disk or disk set on the same channel.
- It also verifies writes on both volume copies.
- If an original disk fails, the duplicate takes over automatically,
without loss of data.
- The NetWare NOS supports as many as eight mirrored disks.
- NetWare's disk-duplexing feature protects against data loss caused
not only by defective hard disks, but also by disk controllers, interfaces,
and power supplies.
- In disk duplexing, all data on one hard disk is duplicated on a second
hard disk on a separate channel.
- This feature automatically detects, corrects, and logs controller
and disk channel faults.
- If any component in a disk channel fails, the redundant channel takes
Transaction Tracking System:
- NetWare uses a Transaction Tracking System (TTS) to protect multiuser
application files from being contaminated by incomplete transactions.
- For TTS files, the NetWare NOS views operations as transactions that
will be either wholly completed or wholly abandoned.
- If a system failure occurs during an incomplete transaction, NetWare
will back out of the transaction and leave the file as it was before the
- The NetWare NOS enables TTS to operate either implicitly or explicitly.
Backup and Restore Services
- The NetWare 3.12 NOS also monitors an optional uninterruptible power
supply attached to the server so that if a power failure occurs, the network
is shut down automatically and safely.