ACE Lab PC-3000 Express - 5.5.4.1. Delicate Work with Non Resident G-List; Diagnostics Using the List of 32 Recent RW Commands

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PC-3000 EXPRESS / UDMA / PORTABLE  Seagate
 ACE Lab F3 architecture
Technical support: ts@acelab.ru
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Attention! All the LBA used above are designated in drive sectors; therefore, if a HDD sector contains 4096 bytes, i.e.
8 host sectors, the ATA LBA should be expressed as Native LBA divided by 8. Furthermore, if a drive's sector size is
other than 512 bytes, LBA = 0 can be shifted by the so-called alignment factor (1 or 0) and by Media Cache size when
it is placed in the beginning of the user data area.
5.5.4.1. "Delicate" work with Non Resident G-List
Translator divergence is often caused by the loss of information about post-processed defects during recalculation
based on P-List. Information from Non Resident G-List in such cases may be lost incompletely. As a matter of fact, in
the simplest case the only operation with Non Resident G-List performed during translator recalculation based on P-
List is clearing of the records counter. The counter value itself in such cases can often be restored from preserved data.
Please note that if Non Resident G-List viewing reveals records flagged differently from 0 (most frequently = 20), it
means that the corresponding information about defects has overwritten during relocation to the list beginning the
original records with the 0 flag initially located there. Moreover, if defects hiding via the translator had been performed,
that operation also caused overwriting of the list beginning. The part that remained intact can be used then to speed up
translator recalculation, especially if the original Non-Resident G-List contained track records. E.g., you can restore the
original overwritten records up to the position where the lists match and then correct the records counter so that the
resulting list includes both the revealed initial records and the final records remaining intact. For better understanding
of the mechanisms involved in manipulations with Non Resident G-List, a description of its structure is appropriate.
Please see the Non Resident G-List dump file below.
0x000000 aa aa 00 00 00 00 00 00 bb bb bb bb cc cc cc cc
0x000010 FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF
0x000020 FF FF FF FF FF FF FF FF 00 00 00 00 00 00 00 00
0x000030 00 10 6E 00 19 00 69 00 C8 00 81 46 F2 7C FF FF
0x000040 33 31 33 46 FF FF FF FF 94 79 08 00 FF FF FF FF
0x000050 FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF
...
0x200040 FF FF FF FF FF FF FF FF 00 FF FF FF FF FF FF FF
0x200050 FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF
...
Two aaaa bytes at offset 0 make up the word of the records counter. The bbbbbbbb (4 bytes) field at offset 8 forms a
double word of the offset for the list of defect locations (PBA). In this example, it is 0x00000048. The next cccccccc
(double word, 4 bytes) field represents the offset of the table containing the flags of defect records. In this example, it is
0x00200048. A single PBA record (4 bytes) corresponds to one byte among the flags; therefore, you can check the size
of PBA records area containing no fill pattern (0xFF) and divide it by 4 to obtain the number of records in Non
Resident G-List. You can verify the assumption by calculating the size of the flags area containing no fill pattern. In the
example above we can see that prior to clearing Non Resident G-List contained one record at LBA = 0x00087994 with
the flag 0. Please keep in mind that Non Resident G-List records describe defects in Native PBA, i.e. they use logical
coordinates based on a single physical sector acting as the measurement unit. You may also encounter FW of the drives
with the approximate capacity of 2TB using a 64-bit PBA field (8 bytes). They can be recognized visually quite easily,
and a check of the occupied portion size in the flags area will allow you to determine conclusively the value of the
records counter field.
5.6. Diagnostics using the list of 32 recent RW commands
You can use the list of 32 last RW commands executed by a drive for diagnostics of its current status. To obtain the list,
you need to enter the utility terminal and toggle the HDD power off and then on, wait for the malfunction to manifest
itself, switch the drive terminal to Online or Diag mode using the [Ctrl]+[R] or [Ctrl]+[Z] commands respectively. Then
send the [Ctrl]+[Х] command, after which the HDD will output a report similar to the following:
ASCII Online mode
ATA 15 Cmds
Ts(ms) dT(ms) Op Cnt LBA
0 99999999 00 0000 000000000000
0 0 00 0000 000000000000
...
0 0 00 0000 000000000000
RW 32 Cmds
Ts(ms) dT(ms) xT(ms) Type Option Mode St EC Info
1098 99999999 1 04 005041 000000 1 00000080 SRV_MEM Type 8 Addr 04001998 Cnt 0004
1099 1 0 04 005041 000000 1 00000080 SRV_MEM Type 6 Addr 0000001D Cnt 0001
1099 0 0 04 005041 000000 1 00000080 SRV_MEM Type 8 Addr 040019A0 Cnt 0004