> Quantum M1800 tape library with
> four SDLT 600 drives, attached via SCSI to a Linux storage node server.
> When I ran jbconfig, I specified
> /dev/nst# where # was 0-3 for each device. I'm wondering what these
> other modes do, and if maybe I should
> be using one of those instead. I'm able to backup and recover fine to
> these drives, but compression rates
> seem low. Here are some of the volumes we've written to:
>
> volume (%used) written
[...]
> FLN027 65% 195 GB
> INC001 full 329 GB
> INC002 full 346 GB
> INC003 full 292 GB
> INC004 full 349 GB
> INC005 100% 355 GB
>
> I thought SDLT II tapes were 300/600. With our old ATL P1000 library
> that has SDLT 220 drives it was not uncommon to get
> 135-160+ GB on a SDLT 1 tape. That's nearly 1.5 times the 110 native
> capacity on average. I'm not seeing anything near 1.5 times
> (let alone twice) the capacity of the SDLT II tapes, however. That would
> be 450 GB.
Yup, but the driver isn't going to control the compression algorithm or
anything like that. If you're getting anything above the native
capacity, then it must at least be enabling compression.
> I copied the stinit.def file template from Quantum's site, and copied it
> to /etc/stinit.def. It has the
> following entry for the SDLT600:
>
> # QUANTUM SDLT600
> manufacturer=QUANTUM model="SDLT600" {
> timeout=3600 # 1 hour timeout
> long-timeout=14400 # 4 hour long timeout
> can-partitions=0
> mode1 blocksize=0 density=0x4A compression=1 # SDLT600 density,
> compression on
> mode2 blocksize=0 density=0x4A compression=0 # SDLT600 density,
> compression off
> mode3 blocksize=0 density=0x49 compression=1 # SDLT320 density,
> compression on
> mode4 blocksize=0 density=0x48 compression=1 # SDLT220 density,
> compression on
> }
There's your 0, 0l, 0m and 0a devices. You certainly want to be using
mode 1. Here's a page that mentions 'stinit -v -v' should show that
association more explicitly (although this file is 1-4 and the other bit
of output is 0-3, I think they should line up).
http://www.mail-archive.com/linux-setup AT senator-bedfellow.mit DOT
edu/msg03128.html
> So am I to assume that nst0, 1, 2 and 3 would use mode 1, and nst0a
> would used mode 2 and
> nst0l would use mode 3 and then nst0m would use mode 4? How do you know
> which mode
> is assigned to which device: nst0, a, l or m? Are we correct to be using
> nst0, 1, 2 and 3 then for hardware compression?
That's my understanding.
--
Darren Dunham ddunham AT taos DOT com
Senior Technical Consultant TAOS http://www.taos.com/
Got some Dr Pepper? San Francisco, CA bay area
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