On Tue, Nov 24, 2015 at 09:27:56PM +0000, David Simpson wrote: ... > > The problem now is throughput. > > My average dump rate is quite poor on the test I've run - I'm not surprised > though as this client is limited by network. This will be made better at some > point by running a test over a separate logical network. > > The average write/throughput to tape (HP LTO6 + Quantum superloader 3 + > Centos7) is around 83 mb/s . That's the best I've seen from my testing so > far. This is with 5x DLEs ranging from around 100 to around 200 GB. I've > been working with that same data. > > Current settings: > LTO6 tape > part_size set to 200GB > chuncksize set to 500mb > holding disk usable 2000GB/2TB > software compression off (Amanda) > hardware compression on (tape) > > record no > strategy noinc > skip-incr yes > auth "ssh" > GNUTAR > > > I'm starting to think more CPU (clock) + striped RAID (for Amanda holding > disk) to feed it would help. What other factors should I look at? > > What are the best ways to tune it? > > Still not convinced about my tape profile (amtapetype). It returned quite a > low speed...
This list has had many posters with difficulties in getting advertised performance out of their LTO systems. Basically the drives have too much performance for their hardware. When I look up your HP drive, it is listed as 1.45TB/hr. Note "B" is bytes, "b" is bits. That ~400MB/sec or 4Gb/sec. For that drive there are 3 possible interfaces, Ultra 320 SCSI, and 2 SAS interfaces corresponding to SATA 2&3. So your interfaces can do 3.2Gb/sec, 3Gb/sec, or 6Gb/sec. Two of them are not even theoretically capable of running the drive at full speed. Which interface are you using? Is the tape drive the only device on its controller interface or must it compete for the controller? This is particularly a problem with SCSI. Are your cables (and terminators) the right type and in good condition? Again SCSI is particularly sensitive. Suppose you have the 6Gb/sec interface. What about the disc drives (particularly the holding disk). When have you seen a disk drive that can match the interface spec? I.e. 600MB/sec. And don't forget, while the holding disk is being read to send data to tape, it is probably also writing multiple amdumps that are still in progress. So yes, a striped RAID is probably a good idea. Getting good performance from an LTO drive will take some effort and probably quality hardware. Unfortunately I've never had the opportunity to try it. Good luck, Jon -- Jon H. LaBadie [email protected] 11226 South Shore Rd. (703) 787-0688 (H) Reston, VA 20190 (703) 935-6720 (C)
