+Q: How can distributions ship a swsusp-supporting kernel with modular
+disk drivers (especially SATA)?
+
+A: Well, it can be done, load the drivers, then do echo into
+/sys/power/disk/resume file from initrd. Be sure not to mount
+anything, not even read-only mount, or you are going to lose your
+data.
+
+Q: How do I make suspend more verbose?
+
+A: If you want to see any non-error kernel messages on the virtual
+terminal the kernel switches to during suspend, you have to set the
+kernel console loglevel to at least 4 (KERN_WARNING), for example by
+doing
+
+ # save the old loglevel
+ read LOGLEVEL DUMMY < /proc/sys/kernel/printk
+ # set the loglevel so we see the progress bar.
+ # if the level is higher than needed, we leave it alone.
+ if [ $LOGLEVEL -lt 5 ]; then
+ echo 5 > /proc/sys/kernel/printk
+ fi
+
+ IMG_SZ=0
+ read IMG_SZ < /sys/power/image_size
+ echo -n disk > /sys/power/state
+ RET=$?
+ #
+ # the logic here is:
+ # if image_size > 0 (without kernel support, IMG_SZ will be zero),
+ # then try again with image_size set to zero.
+ if [ $RET -ne 0 -a $IMG_SZ -ne 0 ]; then # try again with minimal image size
+ echo 0 > /sys/power/image_size
+ echo -n disk > /sys/power/state
+ RET=$?
+ fi
+
+ # restore previous loglevel
+ echo $LOGLEVEL > /proc/sys/kernel/printk
+ exit $RET
+
+Q: Is this true that if I have a mounted filesystem on a USB device and
+I suspend to disk, I can lose data unless the filesystem has been mounted
+with "sync"?
+
+A: That's right ... if you disconnect that device, you may lose data.
+In fact, even with "-o sync" you can lose data if your programs have
+information in buffers they haven't written out to a disk you disconnect,
+or if you disconnect before the device finished saving data you wrote.
+
+Software suspend normally powers down USB controllers, which is equivalent
+to disconnecting all USB devices attached to your system.
+
+Your system might well support low-power modes for its USB controllers
+while the system is asleep, maintaining the connection, using true sleep
+modes like "suspend-to-RAM" or "standby". (Don't write "disk" to the
+/sys/power/state file; write "standby" or "mem".) We've not seen any
+hardware that can use these modes through software suspend, although in
+theory some systems might support "platform" or "firmware" modes that
+won't break the USB connections.
+
+Remember that it's always a bad idea to unplug a disk drive containing a
+mounted filesystem. That's true even when your system is asleep! The
+safest thing is to unmount all filesystems on removable media (such USB,
+Firewire, CompactFlash, MMC, external SATA, or even IDE hotplug bays)
+before suspending; then remount them after resuming.
+
+Q: I upgraded the kernel from 2.6.15 to 2.6.16. Both kernels were
+compiled with the similar configuration files. Anyway I found that
+suspend to disk (and resume) is much slower on 2.6.16 compared to
+2.6.15. Any idea for why that might happen or how can I speed it up?
+
+A: This is because the size of the suspend image is now greater than
+for 2.6.15 (by saving more data we can get more responsive system
+after resume).
+
+There's the /sys/power/image_size knob that controls the size of the
+image. If you set it to 0 (eg. by echo 0 > /sys/power/image_size as
+root), the 2.6.15 behavior should be restored. If it is still too
+slow, take a look at suspend.sf.net -- userland suspend is faster and
+supports LZF compression to speed it up further.