G A L A X Y ® A U R O U R A C O N F I G U R A T I O N A N D S Y S T E M I N T E G R A T I O N G U I D E
85
Section 3 Management
3.1.7
TRACE Details
The details of a ‘Trace’ command is very helpful to support the Aurora. In the
example above,
“
Commands
”
and
“
last 25
”
were chosen from the Config Details screen,
then
a ‘
Display Trace
’
was
taken to capture that data.
The trace shows
the last 25
low-level commands
that
were executed. Above the table is a description of what
the trace has captured
– i.e. commands or all. It shows the total number of entries, how
many it is displaying, and the offset. In the table, on the left, we see the time in hours/minutes.
These will almost never change from one row to the next, unless the array is idle for a long
period of time, has done very few commands, or the commands are taking unusually long to
execute. The entry column shows the number for the particular entry in the Trace file. uGap is
the number of microseconds between commands. uSecs is the amount of time in
Microseconds, that it took to execute the command. User is the originator of the command.
localhost indicates that the array itself requested the command. Lun# is the logical LUN
number of the LUN that the command was performed on. Lun is the name of the LUN that the
command was performed on. CDB describes what command was issued, along with the
length of the CDB (Command Data Block). In the first line, for example, it says “READ10” –
This means the command was a read command, and the command data block for that
command was 10 bytes long. To the right of this a logical LBA. This is the logical block or
sector that the command was told to act on (in this case, read from). The next column is
Length – this is the length of the data that the command was told to act on – in this case, it
was told to read 1024 bytes. Dirty is the number of dirty segments in the cache. Status is the
result of the command as reported by the device – 0 indicates that the command was
successful. A non-zero number indicates the command failed.
In this case, prior to getting to this screen, we specified that we wanted the last 25 commands,
and that commands were shown. If non-commands (All) was chosen, non-commands would
