On Wednesday 08 January 2014 13:13:43 Brian Cuttler did opine: > On Wed, Jan 08, 2014 at 11:18:46AM -0500, Jean-Francois Malouin wrote: > > * Brian Cuttler <br...@wadsworth.org> [20140108 11:09]: > > > Jean-Louis, > > > > > > googled it... I had my numbers wrong, it can supposedly hold > > > 800 Gig, and with HW compression up to 2x that. I should not > > > have to adjust the tape length and no reason (that I can see) > > > for dumps to take more than one tape. > > > > > > Its odd that I'm not seeing an end of media error message... > > > I think I need to run a cleaning tape and keep an eye on this. > > > > I was about to chime in but you bet me to it. > > Indeed LTO4 is 800GB. > > > > Now, did you verify that you're in fact HW not using compression > > enabled? Having both hw and sw compression can actually lead to > > smaller tape usage and waste of cpu cycles. > > I don't know about Solaris but on my Linux servers the command > > tapeinfo from the mtx package will tell me You must pass it the > > generic scsi device of the tape drive. In my case, it's /dev/sg7: > > > > ~# tapeinfo -f /dev/sg7 > > Product Type: Tape Drive > > Vendor ID: 'HP ' > > Product ID: 'Ultrium 4-SCSI ' > > Revision: 'B12H' > > Attached Changer API: No > > SerialNumber: 'HUE084156W' > > ... > > DataCompEnabled: yes > > DataCompCapable: yes > > DataDeCompEnabled: yes > > ... > > Ok, learn something new every day. > > The LTO is advertised as having block level decision making on > compression so that it doesn't expand the data, wonder if that > is not quite true. > > Also - Isn't there another level of tape header that needs to be > cleared? Isn't re-writing the tape with compression off a little > bit of a trick? If you don't clear that other level of header, then > the compression is determined by the header info and not by the > device type selected when you write the tape? > This has been true for me Brian. What I have found that works to shut it off for good:
rewind the tape dd the 1st 32k block to a scratch file rewind the tape. execute the hardware compression off command _for_ _your_ drive. dd that scratch file back to the tape. This must be done on a tape by tape basis. You must not remove the tape from the drive while doing this as if the tape is removed and re-inserted, the drives initial scan of the tape will reset the compression off flags. On a system of the size of yours, having a separate drive to do this in would be a huge help. It would take a while. As a comment only, I found that commodity hard drives were 100's of times more dependable than the tapes and drives I could afford. So I've been using a hard drive for 6 or 7 years now. With a months worth of "tapes" on it, occupy is around 600Gb for me. Tiger-direct sells a cute little drive cage, uses two 5.25 slots in your tower, holds 3 sata drives that can be swapped out hot if offline (but I don't, I do a power down because most of the time I am swapping the 2 top drives around to reboot to another distro), for about a $70 bill. Then 3 <http://www.newegg.com/Product/Product.aspx?Item=N82E16822178271> at $105/copy would give you 6TB for a 2 strip+parity raid, or a 6Tb LVM drive. For $385 or <http://www.newegg.com/Product/Product.aspx?Item=N82E16822148840> at 65 a copy would give you 3 Tb. For nominally $265. So far, I have found that the hardware health monitoring we have has given me plenty of warning about an impending failure to run to town and get a replacement with no losses. Only twice in that same time frame. Be aware though, that most of these "commodity" drives are shipped with alpha or beta firmware, and they will need to be reflashed with the final versions that you can download from Seagate, put on a cd and execute on a linux box to do the drive updates. Now the 64k$ question is how many times would you have to duplicate that to get the capacity you have loaded into the LTO library at a time, and how does that compare when the required offsite and long term storage needs and costs are met? That I can't begin to guess. :( The additional powerdowns of all that storage rotation will impinge on the drives life too, here they spin 24/7 until I need to swap. The other advantage doesn't show up until you need to do a recovery, the hard drives, being random access are about 100x faster than the tape, which must be searched sequentially. I can recover any trashed file on this system in 10 minutes, 8 of which is spent reading the man pages again because I don't do it often enough to remember how! One of the hazards of being an octo something since I'm on my 80th trip around this star now. I hope you kept warm these last 3-4 days. I've virtually hibernated. :) 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) Genes Web page <http://geneslinuxbox.net:6309/gene> Confession is good for the soul only in the sense that a tweed coat is good for dandruff. -- Peter de Vries A pen in the hand of this president is far more dangerous than 200 million guns in the hands of law-abiding citizens.
