I'd thought for both ZFS and the newer (LTO) tape drives that HW-compression was determined on a block by block basic (if enabled) so that expansion of data would not occur.
Granted, this does nothing to help with on CPU usage, but I'd thought it did save, rather, preserve, storage volume. On Wed, May 01, 2013 at 01:41:35PM -0400, Jean-Louis Martineau wrote: > Guy, > > Are you also using amanda software compression? > > Using compression on the holding disk is probably just a waste of CPU as > the data is compressed once and decompressed once, but if it the only > way it can fit in the holding disk. > > If you use amanda software compression, then the data is compressed on > holding disk and on tape. > > Jean-Louis > > On 05/01/2013 01:10 PM, Guy Sisalli wrote: > >I'm attempting to commit 7 TB of text to tape. It's presently stored in > >a natively gzip-9 compressed zvol, weighing in at 1.7 TB. > > > >My holding area is 5 TB, and is set to a native gzip-5 compression. > > > >The functional difference between gzip-5 and gzip-9 is not very much: > >Level 9 compression has a 4-8% advantage over level 5. The entire DLE > >(taken as files, not a snapshot) should fit quite comfortably in my > >holding area. It didn't! > > > >I watched my holding area balloon to 4 TB and keep right on going, as if > >it wasn't compressing at all. Is there any scenario in which this might > >happen? Would you recommend against a setup like the one I've described? > >I'm happy to offer any details needed, but this is probably a good start: > > > >Source: > > > >NAME PROPERTY VALUE SOURCE > >zulu01/keyRepo type filesystem - > >zulu01/keyRepo creation Tue Jan 8 13:48 2013 - > >zulu01/keyRepo used 1.74T - > >zulu01/keyRepo available 6.60T - > >zulu01/keyRepo referenced 1.74T - > >zulu01/keyRepo compressratio 4.65x - > >zulu01/keyRepo mounted yes - > >zulu01/keyRepo quota none default > >zulu01/keyRepo reservation none default > >zulu01/keyRepo recordsize 128K default > >zulu01/keyRepo mountpoint /tank/datastore default > >zulu01/keyRepo sharenfs off default > >zulu01/keyRepo checksum on default > >zulu01/keyRepo compression gzip-9 local > > > >Hold: > > > >NAME PROPERTY VALUE SOURCE > >hold type filesystem - > >hold creation Fri Dec 7 10:34 2012 - > >hold used 257M - > >hold available 5.35T - > >hold referenced 243M - > >hold compressratio 1.00x - > >hold mounted no - > >hold quota none default > >hold reservation none default > >hold recordsize 128K default > >hold mountpoint /hold default > >hold sharenfs off default > >hold checksum on default > >hold compression gzip-5 local > > > --- 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
