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From: Gordon Henderson on 6 Jun 2010 13:52 In article <alpine.DEB.1.10.1006061327440.6621(a)urchin.earth.li>, Tom Anderson <twic(a)urchin.earth.li> wrote: >On Sat, 5 Jun 2010, Gordon Henderson wrote: > >> In article <87631xkevu.fsf(a)araminta.anjou.terraraq.org.uk>, >> Richard Kettlewell <rjk(a)greenend.org.uk> wrote: >>> Andy Botterill <andy(a)plymouth2.demon.co.uk> writes: >>> >>>> I'm writing some scripts to do full and incremental backups for my >>>> computer. My incremental (daily) backup works. However yesterday the >>>> daily backup was 44GB ( I would say 1.4GB is normal but high ). >>>> >>>> Looking at the find instruction I have used -mtime -ctime and -atime. >>>> http://www.brandonhutchinson.com/ctime_atime_mtime.html >>>> The above article implies that I don't really need to monitor -atime. >>>> Is this a safe/sensible thing to do? >>> >>> atime is the time of the last read; you don't need to make a new backup >>> just because atime has changed. >>> >>> Personally I often disable atime completely. >> >> There are still one or 2 things that need it - at least I think there >> is (other than backup programs that is - and I think you need to use >> something like 'dump' so as not to disturb the atime when you read the >> file to archive it). Thinks like email programs I think.. > >There was a big discussion about this on the LKML a while ago, when it was >suggested that atime should be off be default, and there was this relatime >replacement for it. IIRC, it was observed that most systems run perfectly >happily without atime. It's all buried in here: > >http://kerneltrap.org/node/14148 Actually, that's very intersting - I've been using noatime for a long time on archive partitions/drives, but what would be nice to know is what programs actually depends on it - for a file server where you're not using dump, nor running programs that might want to know if a file has been updates (email clients, mutt?) then it's really not needed... Might do some source-code grepping... Or googling - this is nice if you run dovecot... http://wiki.dovecot.org/MailLocation/LocalDisk -> # Dovecot doesn't rely on atime updates, so you can mount the filesystem with noatime Gordon
From: Andy Botterill on 6 Jun 2010 14:20 On 06/05/2010 09:44 PM, Martin Gregorie wrote: > On Sat, 05 Jun 2010 14:57:35 +0000, unruh wrote: > >> Use rsync or rsnapshot to do your backing up. >> > Agreed. rsync is a very fast way of making a backup once the initial copy > has been made. If you want to retain several backup generations (say a > set of three daily backups). This is easy with rsync because it can make > a whole filesystem backup into a specified target directory - simply > rotate your daily backup round a set of root directories. I have changed to using rsync. So far looking good. I'll keep an eye on it for a number of days and then check out spinning the usb external drive down. Thanks Andy > > >> No, almost certainly not. USB power is continuous ( you can plug in a >> flashlight). >> > I think this depends on the USB drive's controller have an old, WD 3.5" > USB drive that powers off on a time-out after its unmounted. I also have > a Formac 2.5" drive that doesn't. > >
From: Richard Kimber on 6 Jun 2010 18:31 On Sat, 05 Jun 2010 10:28:05 +0100, Richard Kettlewell wrote: >> The backup medium is a usb external drive. Eventually I would like to >> only mount the drive for the backup process. Does unmounting >> effectively disable the usb disk (err powering it down)? > > It won't power it down. It depends on the drive. Mine spins down and seems to go to sleep automatically after a certain period of inactivity and I only ever mount it for backup (or restore); but it has its own power supply and so isn't actually powered via USB. It gets woken up via USB when I try to access it. - Richard. -- Richard Kimber Political Science Resources http://www.PoliticsResources.net/
From: unruh on 6 Jun 2010 18:35 On 2010-06-06, Richard Kimber <richardkimber(a)btinternet.com> wrote: > On Sat, 05 Jun 2010 10:28:05 +0100, Richard Kettlewell wrote: > >>> The backup medium is a usb external drive. Eventually I would like to >>> only mount the drive for the backup process. Does unmounting >>> effectively disable the usb disk (err powering it down)? >> >> It won't power it down. > > It depends on the drive. Mine spins down and seems to go to sleep > automatically after a certain period of inactivity and I only ever mount > it for backup (or restore); but it has its own power supply and so isn't > actually powered via USB. It gets woken up via USB when I try to access > it. having it stop spinning is not "power it down". It still draws power ( maybe not quite as much). Thus, if by "power it down" the OP meant "spin down the disks", then as you say many external disks drives do that automatically. > > - Richard.
From: chris on 7 Jun 2010 05:04
On 05/06/10 21:26, Andy Botterill wrote: > On 06/05/2010 08:54 PM, Dave Liquorice wrote: >> On Sat, 05 Jun 2010 14:57:35 GMT, unruh wrote: >> >>>> Does unmounting effectively disable the usb disk (err powering it >>>> down)? >>> >>> No, almost certainly not. USB power is continuous ( you can plug in a >>> flashlight). >> >> True enough, the OP needs to define what he means by "powering it >> down". Does he mean just the disc spun down or all the electronics >> off as well. > > I mean the disc spun down. There appears to be a windows utility to do > that. I do see a few websites which describe regular unix ways to do this. The WD MyBook I have at home does this automatically. No software required. It spins up during boot, but then goes quite after a while. If I want to mount it I need to wait a few seconds for it to spin before it mounts. > At the moment my script is saying most of my personal directory has > changed. I've done something wrong here. I need to fix that before > trying spinning it down. Thanks for the hints. Andy How is the USB drive formatted? If it's FAT32 there as issue with timestamps as FAT does not have the same resolution as ext2/3. I had this issue to and can be worked around with rsync, but I just reformatted to ext3 and now I have no problems. |