Replacing DDS3 with DDS4

[MarkSyder]

Hi everybody,

I'm staying behind after the users have gone today so I can replace an internal DDS3 tape drive with a DDS4.

The drives are the same size and I've got the DDS4 sitting on my desk right now while I wait for the chance to shut the server down.

Rather than wait for things to go wrong (I've never changed an internal tape drive before) I thought it was a good idea to come on here and ask if there are any potential pitfalls to what I plan to do. Also, will the system automatically pick up the new tape drive when I turn it back on?

Mark Syder (like the drink but spelt different)

[John Palmer]

Hi Mark,

I presume that the new drive is compatible with the existing SCSI? If so then just make sure that the SCSI address of the new drive is the same as the old one. The system will identify the new type of drive at reboot.

Regards,
John

[Nick Wickens]

I hit a little issue when I moved from DDS3 to DDS4 last year - one of our data suppliers kept sending data on DAT tapes that were not readable on the DDS4 but were on the DDS4.

This is due to DDS4 not being able to read the first generation DDS 60m tapes (It will read longer DDS1 tapes). So if you have any really old tapes (hey I still have a pile of IBM 3420 tapes but nothing to read them on) then you may not be able to read them.

[MarkSyder]

Hi John/Nick.

Please be patient waiting for your points! It didn't go smoothly on Friday.

I got the old tape drive out without any difficulty, then noticed that the connections on the back were completely different from the new drive.

In complete despondency, I put the old drive back and booted the server back up. As I was on my way out, a colleague pointed out to me that the SCSI cable almost certainly has more than one connector on it and one of them will fit the new drive (I told you this was the first time I'd replaced an internal tape drive!).

I'll have another go this Friday then assign points.

Mark

[Andrew Rutter]

hi, the dds3 will be 50 pin and the dds4 drive will have a 68pin connector on the back. You should have got a 68-50 pin adapter with the drive so you can just connect it to the same ribbon cable.
Also check the patches for the dds4 drive depending upon the OS version. There was a cumulative sam patch to correct the drive been seeing correctly and working with fbackup.

Andy

[Gregory Fruth]

You need to know what type of SCSI bus
is in your machine and what type of SCSI bus
your drive is. You can determine the type
of bus in the machine using ioscan. For
the drive, you need to check the drive's
specs. Presumably the DDS4 is
Ultra160 (LVD) or Ultra320 (LVD), which is
backward compatible with almost all other
SCSI types, EXCEPT Fast Wide Differential
(HVD). If your machine's bus is FWD you
CANNOT use and LVD-type devices on it.
IIRC, FWD was a 50-pin interface, while newer
SCSI types are 68-pin or 80-pin. If you try
to use a 50 to 68 pin adapter, be careful!
Connecting LVD and HVD can cause physical
damage to the SCSI bus and the drive.

[Andrew Rutter]

you are correct to a point gregory,about the scsi bus. However 50 pin scsi connector was always se scsi not FWD which had always been 68 pin. Also dat drives(dds)have only ever been manufactured in SE scsi to my knowledge.
This would mean that mark's existing drive would be SE scsi not FWD.
If an ioscan of the system was done as is, this could easily be checked. If its a HP dds3 drive it most certainly be a C1537A, which is SE scsi.
There could be exceptions to this if it was an external drive in and external enclosure with a scsi bus convertor card inside, but I have never seen one.
I dont think this is the case though.

Mark can you post the ioscan of the tape output so we can see which drive it is you want to replace, and also the model of the machine and if it is an internal one or external dds.

thanks

Andy

[MarkSyder]

ioscan:

10/0/15/0.3.0 tape HP C1537A

New drive model STD2401LW

New drive is a 68 pin.

Mark

[Andrew Rutter]

hi mark,

Yes the C1537A is SE scsi and and the new replacement from seagate is also SE scsi, but u2 capable and backwardly compatible.
Should be able to just swap them over and use the 68-50 pin adapter you should have been supplied with.
You may need to adjust the ID of the drive with the jumpers on the back to avoid any conficts.

Andy

[MarkSyder]

SCSI id shouldn't be a problem - it's set by default to 6, which is free (the old one is 3).

I've set the dip switches for HP-UX, but just read that the new drive is not terminating, so it should not be the last device on the bus. As far as I can see, the old drive is the only device on the bus. Any way round this?

Mark

[Vincent Farrugia]

Hello,

Please put your new DDS4 drive to SCSI ID 3 as well using the jumpers at the rear, so that the hardware path and device files remain the same (this is very important especially if you use backup software or scripts for backup; you would need to change device files for backups to work then).

DDS4 is an LVD device, whereas DDS3 is single-ended (SE). That is why you have one having 50-pin connector and one having 68-pin connector. From experience, you will just need to connect a 50-68 pin converter on your DDS4 and put your SCSI ID the same as the replaced one and it should work. Ioscan should come as CLAIMED with a C5683A instead of C1537A.

This happens because, although DDS4 is LVD, its speed is only 3Mb/s native maximum, which is well within the single-ended limit of 5Mb/s. Therefore, DDS4 will work well on a SE bus without any problems whatsoever.

HTH,
Vince

[Andrew Rutter]

hi mark, heres a link to the web page on terminating your drive.


http://www.certance.com/support/knowledgebase/faq/Drive_Termination_-_Active_vs_Pa


Andy

[MarkSyder]

Hi everybody,

Just to keep you updated - the users can't let me have the server for the next two Fridays.

I thought I'd better let you know in case you thought I was neglecting to give points - you'll get your points as soon as the drive is in the server!

Mark

[Andrew Rutter]

mark,

Did you ever get the tape drive installed and backing up?

just wondered if you were all sorted now.

Andy

[MarkSyder]

Hi Andrew.

Look at my points record ;-)!

No, it's not sorted yet - it didn't come with a converter so I've got one on order. Once it's sorted everyone will get the points they're due.

Mark