keeping in mind that bt4 is based on hardy, i did some sniffing around on this and have a couple of suggestions:
firstly, from here: https://wiki.ubuntu.com/PowerManagement
i found an interesting passage:
there was also this: https://wiki.ubuntu.com/DanielHahler/Bug59695
Unfortunately, ubuntu has mangled disk idling into event handling and power state switching in the past. And this did not deliver idle disks but break disk idling (laptop-mode) features by leaving undefined (factory default) apm settings in place.
To correct disk-idling in Ubuntu Hardy you need to adjust the following:
- Enable CONTROL_HD_POWERMGMT=1 in /etc/laptop-mode/laptop-mode.conf
- ENABLE_LAPTOP_MODE=true in /etc/default/acpi-support (another package's conffile), even if you do not ENABLE_LAPTOP_MODE_ON_BATTERY or _ON_AC in laptop-mode.conf. So that laptop-mode-tools can control the harddisk power management settings.
- (244838 laptop-mode needs to be activated in two places)
- Delete or #comment the four $HDPARM blocks (for...done) in /etc/acpi/power.sh and change the two $LAPTOP_MODE start/stop lines to "$LAPTOP_MODE auto"
- (244836 /etc/acpi/power.sh overrides user settings (fixed in intrepid 250938))
(244831 /etc/acpi/power.sh overrides user scripts (fixed in intrepid 250938))
(244844 Adapt laptop-mode-tools invocation to ubuntu's acpi-support / pm-utils packages (fixed in intrepid 250935))
- Create an empty "laptop-tools" file (touch /etc/pm/power.d/laptop-tools) to override /usr/lib/pm-utils/power.d/laptop-tools.
- (239419 pm-utils has laptop-tools script which conflicts with laptop-mode-tools (not so in intrepid))
With the above changes hardy (ubuntu 8.04) will set the hdparm -B value to 254 when booting and thus override inadequately aggressive hardware defaults that cause load cycling. Not all harddisks will stop head parking with value 255 and some may even overheat. (hdparm -B255 turns off the disk's apm feature, but this only turns off the spin down timer in many disks and doesn't increase the head parking timer at all, which is the issue here.)
Other issues/adjustuments are related to have the hdparm -B value also reset after a suspend/resume cycle (fixed in intrepid 250935).
244833 missing hdparm -B setting during resume
244839 /etc/acpi/start.d and resume.d scripts are not run.
244844 Adapt laptop-mode-tools invocation to ubuntu's acpi-support / pm-tools packages also:
238555 pm-utils doesn't reload hdparm.conf after a suspend
but it lists hardware affected and your specific Toshiba isn't in the list.
however, an interesting troubleshooting step to follow may be to research your hd access with smartmontools.
take a look here for a bit of background from a similar issue:
My experiments with Linux: Harddrive killer bug, workaround for Ubuntu Hardy Heron
you seem to be having the reverse of the issue, but it may very well be related or offer you clues as to what is causing this.
i'm not too sure that this is caused by anything that the BT devs have introduced to the OS from stock, so you may have better luck grep'ing ubuntu/debian forums on this one.
at any rate, if you get this solved please post your solution in case others run into this.
good luck with that...