As long as we are talking about HW vs SW compression, I should say that we've installed pigz, a parallelized version of gzip, on some of our systems with good result. If you have a system that will support it and SW compression is running long you might want to test it out.
On Wed, Aug 24, 2011 at 05:19:44PM -0400, gene heskett wrote: > On Wednesday, August 24, 2011 05:13:46 PM McGraw, Robert P did opine: > > > Gene, > > > > Thanks for your information. > > > > I tried the gzip way but it took too long on my backup server. > > My iron here is beginning to took toward collecting SS one day, but it was > good when I built it from boxes of parts about 4 years ago. Quad core > Phenom running at 2.1Ghz, 4Gb of DDR2 ram. Today that isn't much to brag > about. A typical run here grabs 2 boxes for 36 DLE's, and is done in a > long hour most nights, backing up a bit less than 30Gb most runs. To > vtapes on a 1Tb drive. > > > With my old LTO2 drive I took 90% of the compressed value and used that > > as the length. With "device-property "LEOM" "true"" and part_size > > 40GB, I was getting close to filling my tapes to 100%. > > > > If I ever get a faster backup server I will retry the gizp way again. > > > > Thanks again, > > > No problem Robert, but I did need to emphasize the 'price' of the trade > offs. ;-) > > > Robert > > > > > -----Original Message----- > > > From: owner-amanda-us...@amanda.org > > > [mailto:owner-amanda-us...@amanda.org] On Behalf Of gene heskett > > > Sent: Wednesday, August 24, 2011 10:43 AM > > > To: amanda-users@amanda.org > > > Subject: Re: Do you use this library > > > > > > On Wednesday, August 24, 2011 10:17:33 AM McGraw, Robert P did opine: > > > > JF, > > > > > > > > > > > > Recently you sent me your tapetype for an lto4 drive. I have a > > > > question about the length parameter. > > > > > > > > An lto-4 tape has a non-compress length of ~800GB and in compress > > > > about double. I know these are max values. > > > > > > > > In you answer below you have length set to ~772GB. If I am going to > > > > run in compress mode so should the length value be double or > > > > ~1.4TB. > > > > > > You cannot double compress in normal practice. Feeding a highly > > > compressed > > > file to the lightning fast compression methods used in tape drives > > > will often result in the file growing larger by many percentage > > > points. > > > > > > Gzip can generally beat the tape drives at their own game, albeit at > > > the expense of cpu time to do it right. > > > > > > There are also pretty valid arguments against using the drives > > > compression as it isolates the backup program, preventing it, > > > regardless of the name of > > > the program in question, from keeping track of how much of the tape > > > has been used since the best the programs can do is count the bytes > > > sent down the cable to the drive. If the drive is massaging the > > > data, shrinking or expending it, then the program has no real clue > > > when the tape is full till the drive reports EOT. > > > > > > Because of these considerations, it is pretty universal here that the > > > recommendation is to turn off the drives compressor and let software > > > methods do the data smunching. Then amanda, or any another other > > > program that does track the tape capacity, will then know how much of > > > the tape has been used. > > > > > > This can be very difficult to actually do for those tape formats, most > > > of them, that record the compressor's state in a hidden header file > > > we never see. DDS is one such format where you will have to write a > > > script that: > > > > > > dd reads the first block of the tape out to a file, then > > > mtx re-winds the tape, then > > > mtx turns off the drives compressor, then > > > dd re-writes the first block of the tape with the saved file > > > > > > All without ejecting the tape or going through a tape recognition > > > cycle as most drives do for a freshly inserted tape, and which would > > > turn the compression back on despite your wishes. Only a similar > > > operation will actually turn it of for most drives today if it has > > > ever been turned on and > > > the tape written to. > > > > > > You can of course ignore this advice Robert. > > > > > > > Thanks > > > > > > > > Robert > > > > > > [...] > > > > > > Cheers, gene > > > -- > > > > > > "There are four boxes to be used in defense of liberty: > > > soap, ballot, jury, and ammo. Please use in that order." > > > > > > -Ed Howdershelt (Author) > > > > > > He's dead, Jim. > > > Cheers, gene > -- > "There are four boxes to be used in defense of liberty: > soap, ballot, jury, and ammo. Please use in that order." > -Ed Howdershelt (Author) > > The covers of this book are too far apart. > -- Book review by Ambrose Bierce. --- 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. 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