Rory, On Wed, Jan 05, 2011 at 12:00:40PM -0500, rory_f wrote: > I want to ensure tapes are filled 100% each time where possible. I've > written a script in python to look at directory, figure out size, and > create a disklist which will ensure a round about size for each disklist > file - so for instance it will try to create a disklist file that contains > entries in groups of 400gb's - the size of a tape. I know amanda will fill > a tape to 100% where possible but sometimes, if it is using compression, > this doesn't work, and the first two tapes will fill 500gb+ and then the > last tape will be left with 200gb. This is a waste of 200gb - I'm trying > to make sure all tapes are full where possible and not waste any space.
I'm not certain I understand your example. If you have 12000 GB to write and you write 500 gb to the first two tapes and 200 gb to the last tape you are using the same three tapes you'd use if you wrote 400 gig to each. You either waste the space equally at the end of all three tapes or all at ones on the last tape. If a tape will hold 500 gig and you only put 400 gig the tape isn't full. This "overfull" is a hazard of HW compression that you don't experience with SW compression. If you know from experience that your data will compress by 20% and you have a 400 gig tape and you are using HW compression you can lie in the tapetype definition and claim its a 500 gig tape so amanda will be able to estimate usage better, but its not going to be an exact fit because even with SW compression where amanada can track the data there is always a little real-life flux in the data compression (unless of course the data is static, in which case you might want to archive it rather than back it up). There are settings within amanda that help to fill tapes. Admittedly I've only used "taperalgo" and have been very happy with the "largestfit" setting, but there are also the values flush-threshold-dumped flush-threshold-scheduled taperflush which have examples settings in the amanda.conf file. These settings should help you fill tapes, will even delay flushing of the work area to tape if the tape is not expected to be filled. For my money the more you can delegate to amanda and the less fiddling with the disklist or other files the better. > I know I could take the tape that is half full and archive the contents again > with added content but this is time consuming. > > I just want to make sure amanda is working with my script to make sure all > tapes are being filled. Yah... but you can't fill them by not filling them. > Do you see what i'm getting at? I think so, do you see where I'm going ? > Thanks, your welcome, Brian > Brian Cuttler wrote: > > Rory, > > > > When I am using tape compression I often...sorry. > > > > When using SW tape compression amanda will know what the > > typical compression is for any given DLE and will (I believe) > > use the expected compressed size of the data when estimating > > overall tape usage. > > > > When I use HW compression I often lie about the tape length, > > extending the actually physical size by the expected compression > > amount so that I am able to utilize the full physical tape. > > This is very valuable for me in the couple of cases where I > > have a non-spanning DLE that is larger than the physical tape > > would be without compression, else amanda would report that the > > DLE was larger than the tape... > > > > What goal/outcome are you seeking ? > > > > Brian > > > > On Wed, Jan 05, 2011 at 11:34:47AM -0500, rory_f wrote: > > > > > Hey, > > > > > > So I've noticed that sometimes Amanda will fill up a tape with more than > > > 400gb (LTO3) - I'm assuming this is down to compression? Is there another > > > way to limit this from happening apart from turning hardware and software > > > compression off? > > > > > > Thanks, > > > > > > +---------------------------------------------------------------------- > > > |This was sent by rory < at > mrxfx.com via Backup Central. > > > |Forward SPAM to abuse < at > backupcentral.com. > > > +---------------------------------------------------------------------- > > > > > > > > > > > --- > > > > > +---------------------------------------------------------------------- > |This was sent by r...@mrxfx.com via Backup Central. > |Forward SPAM to ab...@backupcentral.com. > +---------------------------------------------------------------------- > > --- Brian R Cuttler brian.cutt...@wadsworth.org Computer Systems Support (v) 518 486-1697 Wadsworth Center (f) 518 473-6384 NYS Department of Health Help Desk 518 473-0773 IMPORTANT NOTICE: This e-mail and any attachments may contain confidential or sensitive information which is, or may be, legally privileged or otherwise protected by law from further disclosure. It is intended only for the addressee. If you received this in error or from someone who was not authorized to send it to you, please do not distribute, copy or use it or any attachments. Please notify the sender immediately by reply e-mail and delete this from your system. Thank you for your cooperation.
