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Following are questions and answers
from an actual questions and answers from a Applications User's
Handbook Seminar:
If you would like to submit a question that is not included here,
please email us at Tech
Support
1) Does LMS remap data without warning
the Host?
YES. If the media management
area is corrupted or maps cannot be read, a new map will be written
that points to alternates that are in the media management area.
However, the alternate data will never be rewritten.
2) Which write command does LMS recommend
(Opcode 2ah or 2eh)?
LMS recommends the write
with verify command be used (Opcode 2eh).
3) How does the driver know that a write
error has occurred?
A check condition status
will be reported on the write with either a media or hardware error
sense key.
4) What internal actions are performed
to prevent a write fault?
The RWS PCA can report an
error during a write or the LaserDrive can fail the verify pass
on written data. In either case, the LaserDrive will rewrite the
data in the alternate area of the media management section of the
media four times before a write fault is reported.
5) Will the LaserDrive post firmware
revision levels in the AEL?
Yes.
6) What will be the performance hit
caused by the recommended implementation of the SEW table?
About 500 ms when mounting
the media.
7) How big is the data buffer?
12.8 Mbytes
8) How big is the read ahead buffer?
All the data buffer will
be used.
9) Does the LaserDrive have write caching?
No.
10) Does the write to disk wait until
the SCSI write (to data buffer) transfer is complete?
Yes. Each write burst must
complete before data is written to the disk unless the burst size
is bigger than the buffer. In this case, when the data buffer is
about 90% full data will be written to the media so that buffer
space can be freed up to continue the write burst.
11) What is returned if a Start command
is sent to a LaserDrive that is ready?
Good status.
12) Will read retries be exhausted on
a read command that runs into a blank sector?
No, unless there is a media
defect that causes some other error such as tracking loss.
13) How will a LaserDrive respond to
a TUR during spin-up?
Busy status will be returned
if the LaserDrive is in self test. Otherwise, check condition status
will be returned until the LaserDrive becomes ready.
14) What is the recommended action if
the LaserDrive hangs in spin up?
Reset the LaserDrive. If
this doesn't work cycle power.
15) How many sectors will be rendered
useless in the event of a reported write fault?
The driver should assume
that all the sectors for that write command are now unreadable,
and rewrite the data elsewhere on the media.
16) How is the last map address saved
to NV RAM on a power failure?
It is not saved. This map
is reconstructed by reading in the unmapped alternates in the media
management area of the media.
17) Is there a way to determine which
side of the media an LBA is located on?
Yes. Use the Read Sector
Location Command.
18) If a read is aborted, will the read
ahead cache abort?
Yes.
19) On a read, does the data transfer
wait for the extent to be satisfied to the data buffer or buffer filled
condition to begin the SCSI data transfer?
The SCSI data transfer will
begin when the Mode Select Maximum burst length, read command length
or buffer 90% full condition has been reached, whichever, is smaller.
20) How are bad blocks handled during
a Media Scan command?
These blocks will be reported
as a read error unless the ignore errors bit is set in the media
scan command. If the ignore errors bit is set these block will be
treated as written.
21) How can a Host tell whether an LM
6000 or LM 8000 media is installed in a LaserDrive?
By using the Read Capacity
command.
22) Will the LaserDrive report LM 8000
media installed?
Yes, through extended sense
data byte 32h in the LM 8000 mode.
23) Explain how the LaserDrive will
write protect the media during map write faults?
When excessive map write
faults occur on a piece of media or with a LaserDrive a special
error will be reported and all write to the media will receive a
check condition status with this error. Sense Key 03h, ASC 32h,
byte 18 will be a 39h. This error can be cleared after the LaserDrive
has been serviced by pressing the self test button or clearing NV
RAM through the DOC.
24) Is there a performance increase
when reading an LM 6000 media on a 8000 LaserDrive?
No, the media still spins
at the same rate as if inserted into a 6000 Drive.
25) Are LaserDrive configuration parameters
saved through a firmware download?
Normally, yes. However,
some firmware changes may change the location of data in NV RAM
and configuration data may be lost. In general, it is best to always
restore all parameters after every firmware download.
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