topic Re: SCSI Question in Operating System - HP-UX

SCSI Question

Tom Jackson — Wed, 08 Jan 2003 15:33:16 GMT

Hi:

I have a J6000 workstation with two LVD 36 GB internal disks and two LVD 36 GB external disks. The two external disks are connected to the external SCSI LVD/SE port. Currently, the two external disks are mirroring the system and data disks for backup purposes. I don't have mirror software. I run a cron job each night to dd the disks.

I don't have a tape drive on the system, and management wants my support group to find a tape backup device that is not being used rather than purchasing a DLT.

Questions: Can/should I connect a non-HP SE SCSI tape drive to the external LVD/SE SCSI? I've read that mixing SE and LVD devices will cause a reduction in device performance. Will this only occur if an SE device is in use? Should I have any other concerns?

I also want to connect a cdrom to the same external SCSI bus. Can you believe it, no cdrom either. : (

I know a PCI SCSI card is less than $600, but I can't get any money!

All comments welcome.

Tom

Re: SCSI Question

Chris Wilshaw — Wed, 08 Jan 2003 15:40:54 GMT

Using fbackup, you could always back it up to a remote drive

fbackup -vf remote_server:device_path .......

Re: SCSI Question

Eugeny Brychkov — Wed, 08 Jan 2003 15:46:25 GMT

Tom,
as soon as you connect SE device to LVD bus whole bus becomes SE - 5(10-wide)mb/s, 6 (3) meters.
You can connect any interface compatible device as external device. Internal devices can be supported by HP only.
I guess this workstation should have internal SE bus for CD-ROM and tape drive. Consult user's manual.
Please consider DAT40 device (SE), but if it will not be sufficient to hold your data you should consider buying DLT/LTO drive (they can be LVD!)
Eugeny

Re: SCSI Question

Dietmar Konermann — Wed, 08 Jan 2003 15:50:14 GMT

If you attach an SE only device then the whole bus falls back to use SE. With all ristrictions, cable length, e.g... not only during use. Not a good idea.

Best regards...
Dietmar.

Re: SCSI Question

melvyn burnard — Wed, 08 Jan 2003 15:54:04 GMT

With all due respect to your management, just ask them the costs involved if your backups are NOT available and do NOT work, due to the way you are looking to do the backups "saving money".

From experience I have seen far too many people/companies being what we call Penny wise but pound foolish

Re: SCSI Question

Tom Jackson — Wed, 08 Jan 2003 15:59:14 GMT

Hi:

Thanks for the replies!

Chris:

Network backup has been considered, but is not available. Thanks anyway!

Eugeny:

When the bus speed goes down will the disks still function?

The cdrom interface is IDE; no internal scsi for cdrom or tape drive. Also, only two disk devices can connect to the internal scsi.

I had HP configure a backup solution, and they recommended adding a PCI scsi adapter.

Tom

Re: SCSI Question

MANOJ SRIVASTAVA — Wed, 08 Jan 2003 16:02:47 GMT

Hi Tom

You can connect a non HO SE SCSI tape drive , the reduction in device perfomence is there but again that is not so significant becasue in any case you are using a sloe device like a tape drive and not a disk . I would prefer if you run the backups in offtime hours like you are running your dd . Well a CDROM drive has a similar story .

Manoj Srivastava

Re: SCSI Question

melvyn burnard — Wed, 08 Jan 2003 16:03:57 GMT

Tom
I know it means spending money, but in hte long term it is the better solution.
I would also recommend you take a look at the Ignite/UX tool which is a free software utilty, (that will cheer up your management )
allowing you to create a bootable recovery tape in hte event you lose ALL the disks etc.

Re: SCSI Question

Tom Jackson — Wed, 08 Jan 2003 16:15:17 GMT

Hi Melvyn:

I appriciate your comments and whole heartedly agree! Management wants to MAKE SURE we don't have hardware collecting dust that can give me a backup solution. If I can't get any existing HW to function, I think they will get the $12,000 I need for the DLT, SCSI adapter, CDROM, tapes and cables.

My mirror disk script works very well. I've had to boot from the mirror several times to save my rear end. Management considers my mirror process a single day backup, as well as protection from single disk failure.

I've used ignite and it is sweet! Do you know if non-HP tape drives with enough capacity will function with ignite?

Tom

Re: SCSI Question

Gregory Fruth — Wed, 08 Jan 2003 22:33:34 GMT

In Single-Ended mode the bus signals may
not be strong enough to reach the end of
the cable. That's why the max cable length
in SE mode is 3 meters vs. 12 meters in
LVD mode. If you attach an SE-only device
to an LVD chain the devices may not work
properly if the cabling is too long.

Also, in SE mode you may not be able to use
more than 4 devices on the bus (including the
SCSI controller). See the table at:
http://www.scsita.org/terms/scsiterms.html

As for the CD-ROM, are you trying to say
that there's no internal CD-ROM device?
Surely the J6000 has an external SE bus.
You should probably attach CD-ROM and
DDS devices to that.

Re: SCSI Question

Tom Jackson — Thu, 09 Jan 2003 13:05:11 GMT

Hi Greg:

You are correct, according to the Technical Reference HP Visualize J6000 Workstations online manuals, the max bus length is 3 meters if the bus is in SE mode and there are 1-4 devices on connected to the bus (including the controller). If there are 5-8 devices on the bus the total length of cable should not exceed 1.5 meters. Hmmm.

The J6000 has one external LVD/SE SCSI. It currently has two 10K disks connected.

I thought I read somewhere that there are priorities associated with the SCSI bus ID number. Does anyone know where I can find this information?

Tom

Re: SCSI Question

Eugeny Brychkov — Thu, 09 Jan 2003 13:18:08 GMT

Priorities:
Highest... 7-6-5-4-3-2-1-0-15-14-13-12-11-10-9-8 ... Lowest
That's why controllers usually have SCSI Id=7 - this Id has highest priority
Eugeny