Veritas-bu

[Veritas-bu] Drive Type

2006-07-19 05:10:05
Subject: [Veritas-bu] Drive Type
From: Asiye.Yigit at gantek.com (Asiye Yiğit)
Date: Wed, 19 Jul 2006 12:10:05 +0300
Hi William,
Thank you so much  for your explanation. It is very helpful. 

Asiye 

-----Original Message-----
From: william.d.brown at gsk.com [mailto:william.d.brown at gsk.com] 
Sent: Wednesday, July 19, 2006 12:03 PM
To: Asiye.Yigit at gantek.com
Cc: veritas-bu at mailman.eng.auburn.edu;
veritas-bu-bounces at mailman.eng.auburn.edu
Subject: Re: [Veritas-bu] Drive Type


I'm fairly sure that the HCART vs HCART2 has no effect on density etc.
The 
settings for this are controlled in a couple of places, but relate to
the 
configuration of the drive at the OS level.

At the UNIX OS level there are several device files created, with 
different characteristics - all compatible with the drive.  There will 
normally be a "no-rewind" set which have to be used for NetBackup, but 
there will also often be ones with and without compression enabled.
You 
see similar with a NetApp, it will offer a set of devices with
differrent 
capacities for the same physical drive, so when you set up an NDMP drive

on  a NetApp you pick the one that gets the most on the tape.

The st.conf is used to map the SCSI answerback string of the drive to a 
set of configuration parameters.   The answer string must be an exact 
match to what the drive sends, but you may be able to play around with
the 
configuration options that are matched to it.    You can enable fixed 
block size quite simply (but don't!), but there is a bitmask that is I 
think sent to the drive that will affect how it behaves.  I would be 
fairly sure that this is where you would have to tinker if you wanted to

make say an LTO3 write at LTO2 density on an LTO3 tape - if it is even 
capable of doing so.  I think this is used for the SCSI 'Mode Select' 
command.  In general I would avoid touching these values.

>From what you say you don't actually *want* to do any of that!

Otherwise, as Simon and others have said, all that matters is the media 
type and drive type as NetBackup knows them must match or it will not
load 
the tape.  For example although an LTO3 drive can read and write LTO2
tape 
(and does it faster than an LTO2 drive), NetBackup has no way to set 
backwards read/write compatibility rules.  BackupExec does!

So if the only LTO you have is LTO3, feel free to call them HCART - 
otherwise when LTO6 comes you will have to call them HCART2 or something

silly.  It really is just a name.

William D L Brown




"Asiye Yi?it" <Asiye.Yigit at gantek.com> 
Sent by: veritas-bu-bounces at mailman.eng.auburn.edu
18-Jul-2006 20:09
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[Veritas-bu] Drive Type






Hi All,
I have a question. Is the NetBackup adjusting density according to the
drive type? I mean if I set drive density to hcart2 for hcart3 drive,
what would the capacity for that media? Is it like hcart3 regardless of
the setting in netbackup?

Regards,


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