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SubjectRe: Burning multiple DVDs at one time
On Mar 15 Wakko Warner wrote:
> I'm having problems doing this.
> When I burn a single disk, wodim shows the drive buf @ 99% consistently.
> The instant that a 2nd disk is being burned, the drive buf on the first one
> starts to drop and data stops when the 2nd wodim is performing OPC.
> During the burn of both discs, the drive buf will drop on both until one of
> them finishes. Both drives see under runs.
> When one starts fixating, the other will hang until the fixation is
> completed.
> During the burns, the fifo of both never drop below 99%
> There are no logs that are produced.
> My burners are:
> [6:0:0:0] cd/dvd ATAPI iHAS422 8 4L11 /dev/sr7
> [7:0:0:0] cd/dvd ATAPI iHAS224 B GL05 /dev/sr8
> Both are SATA drives attached to the onboard sata controller
> 00:1f.2 SATA controller: Intel Corporation 631xESB/632xESB SATA AHCI Controller (rev 09)
> 00:1f.2 0106: 8086:2681 (rev 09)
> The kernel is a vanilla kernel v3.0.0. (This also happened with 2.6.35)
> I don't believe it matters, but the data is coming over NFS via gigabit
> ethernet. Each burn process uses a 768M host buffer. As I stated, the host
> fifo on wodim never goes below 99%
> The system motherboard is a SuperMicro X7DA8

This is likely due to serialization by a global mutex in the sr driver.
Have a look at thread "[PATCH] [SCSI] sr: fix multi-drive performance,
remove BKL replacement" from February.
Stefan Richter
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