[stgt] Problem with dvd burner

[Frank Michel]

Hello,

We are encountering some problem while configuring a sata dvd burner
for remote access using tgtd 1.0.15  "passthrough" mode.
It looks like access to the remote device is unreliable : sometime it
works, sometime not, and in all situations we are receiving strange
messages from the kernel.

Apr 20 10:43:20 pisd kernel: ata2.00: exception Emask 0x0 SAct 0x0
SErr 0x0 action 0x6 frozen
Apr 20 10:43:20 pisd kernel: sr 1:0:0:0: [sg1] CDB: Write(10): 2a 20
00 00 00 00 00 00 1f 00 00 00 00 00 00 00
Apr 20 10:43:20 pisd kernel: ata2.00: cmd
a0/01:00:00:00:f8/00:00:00:00:00/a0 tag 0 dma 63488 out
Apr 20 10:43:20 pisd kernel:         res
40/00:02:00:0c:00/00:00:00:00:00/a0 Emask 0x4 (timeout)
Apr 20 10:43:20 pisd kernel: ata2.00: status: { DRDY }
Apr 20 10:43:20 pisd kernel: ata2.00: hard resetting link
Apr 20 10:43:20 pisd kernel: ata2.01: hard resetting link
Apr 20 10:43:22 pisd kernel: ata2.00: SATA link up 1.5 Gbps (SStatus
113 SControl 300)
Apr 20 10:43:22 pisd kernel: ata2.01: SATA link down (SStatus 0 SControl 300)
Apr 20 10:43:22 pisd kernel: ata2.00: failed to IDENTIFY (I/O error,
err_mask=0x2)
Apr 20 10:43:22 pisd kernel: ata2.00: revalidation failed (errno=-5)
Apr 20 10:43:27 pisd kernel: ata2.00: hard resetting link
Apr 20 10:43:28 pisd kernel: ata2.01: hard resetting link
Apr 20 10:43:28 pisd kernel: ata2.00: SATA link up 1.5 Gbps (SStatus
113 SControl 300)
Apr 20 10:43:28 pisd kernel: ata2.01: SATA link down (SStatus 0 SControl 300)
Apr 20 10:43:28 pisd kernel: ata2.00: configured for UDMA/100
Apr 20 10:43:28 pisd kernel: ata2: EH complete

The frozen and timeout message appear nearly all the we access the
drive remotely, even though there is no error reported.
In the previous syslodg extract, the revalidation problem is the usual
symptom for dvd burning error.
The drive does't show such errors when accessed locally.

When it works, we can burn dvd up to 4x. We never succeeded to burn a
faster media (12x, 16x)

Is there a way we can troubleshoot the problem using tgtd debug trace system ?
Our configuration is RHEL 6,  with stgt v1.0.15, 12 GB RAM and core I7.

Thanks for your help,
Frank MICHEL
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