On Fri, Jan 16, 2004 at 05:16:11PM -0500, Alastair Neil wrote:
> Yes I was aware, I thought using the device file without the "c" in it
> implied no compression. I have searched in vain for information about
> how to turn off compression.
>
> On Fri, 2004-01-16 at 17:05, donald.ritchey AT exeloncorp DOT com wrote:
> > Alastair:
> >
> > I use the same drive on HP/Compaq Tru64 UNIX.
> >
> > 1. Do NOT use the hardware compression. See the archived for an
> > exhaustive discussion of this topic.
> >
> > 2. Uncompressed capacity of this drive is around 40 GB +/- 2GB.
> >
> > Using a compressed tape device which uncompressible data will actually
> > reduce capacity, since recompressing compressed data makes it expand.
> >
> > Best wishes,
> >
> > Don
> >
> > Donald L. (Don) Ritchey
> > E-mail: Donald.Ritchey AT exeloncorp DOT com
> >
> >
> > -----Original Message-----
> > From: Alastair Neil [mailto:aneil2 AT gmu DOT edu]
> > Sent: Friday, January 16, 2004 2:17 PM
> > To: 'amanda-users AT amanda DOT org'
> > Subject: amtapetype
> >
> >
> > I just ran amtypetype -f /dev/rmt/0bn, a Sun Storedge L9 autochanger
> > and recieved the following:
> >
> > define tapetype unknown-tapetype {
> > comment "just produced by tapetype prog (hardware compression on)"
> > length 34169 mbytes
> > filemark 28 kbytes
> > speed 1787 kps
> > }
> >
> > I'm confused because I believed this to be a DLT8000 drive which should
> > be closer to 80 MBytes compressed, and certainly the speed is not what I
> > expected either. I ran amtypetape -c -f /dev/rmt/0bn and amtypetape -c
> > -f /dev/rmt/0cbn and received nearly identical output:
> >
> > amtapetype -c -f /dev/rmt/0cbn
> > Writing 256 Mbyte compresseable data: 27 sec
> > Writing 256 Mbyte uncompresseable data: 56 sec
> > WARNING: Tape drive has hardware compression enabled
> > Estimated time to write 2 * 1024 Mbyte: 448 sec = 0 h 7 min
> > amtapetype -c -f /dev/rmt/0bn
> > Writing 256 Mbyte compresseable data: 25 sec
> > Writing 256 Mbyte uncompresseable data: 56 sec
> > WARNING: Tape drive has hardware compression enabled
> > Estimated time to write 2 * 1024 Mbyte: 448 sec = 0 h 7 min
> >
> > Host is a Sun E250, with HVDS adaptor.
> >
> > Does anyone have experience with this drive?
>
For info on the device driver, check the ref manual for the "scsi tape" driver.
man 7 st
Ususally I would point you to /kernel/drv/st.conf for more info. But when I
went to look, it does not give the data you might want for a DLT-8000. Instead
it says:
# For the following drives which are configured automatically,
# no entry is needed in st.conf:
...
# Quantum DLT8000
<Non-Solaris Users Yawn and Turn Off Now>
Basically the driver changes parameters by selecting a name in /dev/rmt.
You have six primary choices and two flags. Assuming drive 0, the primary
ones are 0, 0l, 0m, 0h, 0c, and 0u. In reality, there are fewer choices,
a maximum of four. That is the number of specifications available in st.conf.
Some of the six choices may link to the same /device entry. In fact, all six
could be the same. That is the kind of info that st.conf might have given you.
0 would be the default and always is the same as another. By changing st.conf
you can modify which it is (at least you could if your drive used st.conf :)
0c and 0u are always the same; historical reasons I guess for keeping both.
My drive uses "l" for "low density" and turns off compression.
Again, for my drive, as you assumed, "c" (and "u") are turn on compression.
But from drive to drive, neither of those is a given. My "m" ("medium density")
leave the drive in whichever compression mode it was in. And I have not figured
out what "h" ("high density") does. Seems to be compression on, but is not the
same device as c&u.
The flags are:
n Do not rewind after closing the tape drive
b Use Berkeley (BSD) style end of file handling rather than System V
(AT&T).
The no-rewind flag is of course important when using amanda.
The "b" flag should not be needed. Amanda tries to be coded to handle both
types
(only in a few places would it matter) but in general I think the default (AT&T)
style is what is assumed.
HTH
</Non-Solaris Users Yawn and Turn Off Now>
--
Jon H. LaBadie jon AT jgcomp DOT com
JG Computing
4455 Province Line Road (609) 252-0159
Princeton, NJ 08540-4322 (609) 683-7220 (fax)
|
