Date: Thu, 9 Apr 1998 10:26:53 -0600 (MDT) From: "Kenneth D. Merry" <ken@plutotech.com> To: ip@mcc.ac.uk Cc: scsi@FreeBSD.ORG Subject: Re: compression on Exabyte 8700LT? Message-ID: <199804091626.KAA07550@panzer.plutotech.com> In-Reply-To: <199804091527.QAA09483@albatross.mcc.ac.uk> from Ian Pallfreeman at "Apr 9, 98 04:27:31 pm"
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Ian Pallfreeman wrote...
> I've recently acquired another Exabyte drive, an 8700LT. This drive claims to
> be able to write 10Gb to a 112m tape in compressed mode, but I'm getting just
> the 5Gb I'd expect uncompressed.
>
> There are no switches other than the SCSI id on the box. The manual tells me
> to enable compression in software. ``mt -f /dev/rst1 comp 1'' logs the error
> "select returned an error of 5" to the console and gives me an I/O error from
> mt(1).
>
> How do I permanently enable compression?
>
> FreeBSD 3.0-CURRENT #9: Thu Apr 9 16:06:09 BST 1998
> ip@lurch:/usr/src/sys/compile/LURCH
> [...]
> ahc0: <Adaptec 2940 Ultra SCSI host adapter> rev 0x00 int a irq 9 on pci0.19.0
> ahc0: aic7880 Single Channel, SCSI Id=7, 16/255 SCBs
> [...]
> st0 at scbus0 target 4 lun 0
> st0: <SONY SDT-5000 3.30> type 1 removable SCSI 2
> st0: Sequential-Access density code 0x13, drive empty
> st1 at scbus0 target 5 lun 0
> st1: <EXABYTE EXB-8505 0051> type 1 removable SCSI 2
> st1: Sequential-Access density code 0x0, drive empty
Well, this may be fixed by PR kern/5274. Basically, the page
format bit isn't being set when a mode select is done on the drive, so the
drive probably thinks it's a SCSI-1 mode select, and doesn't pay attention
to the compression page.
So, you might want to try applying the patch in that PR, and see if
it fixes your problem. Most drives I've seen come with compression turned
on by default, but maybe yours doesn't.
The next CAM snapshot fixes this. (at least on the 6 tape drives
I've tested it on) mt(1) will tell you whether compression is supported or
turned on for your drive. (and which type of compression is in use) For
instance:
sa0 at ahc0 bus 0 target 5 lun 0
sa0: <ARCHIVE Python 25601-XXX 2.63> Removable Sequential Access SCSI2 device
sa0: 5.0MB/s transfers (5.0MHz, offset 15)
{bladerunner:/usr/home/ken:4:0} mt status
Mode Density Blocksize bpi Compression
Current: X3B5/88-185A 512 bytes 61000 unsupported
---------available modes---------
0: X3B5/88-185A 512 bytes 61000 unsupported
1: X3B5/88-185A 512 bytes 61000 unsupported
2: X3B5/88-185A 512 bytes 61000 unsupported
3: X3B5/88-185A 512 bytes 61000 unsupported
sa1 at ahc1 bus 0 target 4 lun 0
sa1: <EXABYTE EXB-8500-85Qanx0 0415> Removable Sequential Access SCSI2 device
sa1: Serial Number 00263194
sa1: 4.32MB/s transfers (4.32MHz, offset 11)
{bladerunner:/usr/home/ken:7:0} mt -f /dev/nrsa1 status
Mode Density Blocksize bpi Compression
Current: 0x00 1024 bytes 0 unsupported
---------available modes---------
0: 0x00 1024 bytes 0 unsupported
1: 0x00 1024 bytes 0 unsupported
2: 0x00 1024 bytes 0 unsupported
3: 0x00 1024 bytes 0 unsupported
sa2 at adv1 bus 0 target 2 lun 0
sa2: <EXABYTE EXB-85058HE-0000 0076> Removable Sequential Access SCSI2 device
sa2: Serial Number 16012000
sa2: 5.0MB/s transfers (5.0MHz, offset 15)
{bladerunner:/usr/home/ken:9:0} mt -f /dev/nrsa2 status
Mode Density Blocksize bpi Compression
Current: 0x00 1024 bytes 0 IDRC
---------available modes---------
0: 0x00 1024 bytes 0 IDRC
1: 0x00 1024 bytes 0 IDRC
2: 0x00 1024 bytes 0 IDRC
3: 0x00 1024 bytes 0 IDRC
sa0 at ahc0 bus 0 target 5 lun 0
sa0: <SONY SDT-5000 3.02> Removable Sequential Access SCSI2 device
sa0: 5.0MB/s transfers (5.0MHz, offset 8)
{thunderdome:/usr/home/ken:5:0} mt status
Mode Density Blocksize bpi Compression
Current: X3B5/88-185A 512 bytes 61000 DCLZ
---------available modes---------
0: X3B5/88-185A 512 bytes 61000 DCLZ
1: X3B5/88-185A 512 bytes 61000 DCLZ
2: X3B5/88-185A 512 bytes 61000 DCLZ
3: X3B5/88-185A 512 bytes 61000 DCLZ
For some reason, Exabyte drives don't like to report any density
information. Go figure.
Ken
--
Kenneth Merry
ken@plutotech.com
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