In the message dated: Mon, 05 Mar 2012 11:05:28 EST,
The pithy ruminations from John Drescher on 
<Re: [Bacula-users] LTO media type mixup> were:
=> On Mon, Mar 5, 2012 at 10:44 AM, Tilman Schmidt
=> <t.schmidt AT phoenixsoftware DOT de> wrote:
=> > Am 05.03.2012 15:43, schrieb Alan Brown:
=> >> On 05/03/12 14:17, Adrian Reyer wrote:
=> >
=> >>> Well, 'Media Type' is misleading. It is more a 'Media Group'. every
=> >>> medium in the same group can be requested on every SD that support that
=> >>> 'Media Group'. It doesn't actually have anything to do with the mediums
=> >>> capabilities/size.

Good explanation. I'd strongly support changing the name of the directive in
the configuration file to something like "Media Group".

=> >>
=> >> To add confusion, any given bacula drive can only support one media type.
=> >>

Yeah.... I guess it would make sense if "Media Group" was a list of supported
strings, not a single value.

In this model, sites with multiple devices (tape libraries, disk storage
arrays, etc) could use multiple media types, with each physical device being
assigned a list of media types (in a "Media Group") that the device can use.
Furthermore, the device definition in bacula-sd.conf could list properties for
each media type. For example:

        Device {
                Name = lto5-changer
                Media Group = LTO3, LTO4, LTO5
                Media Options {
                        LTO3 = ReadOnly
                        LTO4 = ReadWrite
                        LTO5 = ReadWrite
                }
        }
        Device {
                Name = lto4-changer
                Media Group = LTO2, LTO3, LTO4
                Media Options {
                        LTO2 = ReadOnly
                        LTO3 = ReadWrite
                        LTO4 = ReadWrite
                }
        }
        Device {
                Name = File
                Media Group = localNAS, remoteNAS_for_DR
                Media Options {
                        localNAS = ReadWrite
                        remoteNAS_for_DR = ReadOnly
                }
        }

=> >> The only way around this problem is to define extra drives for each
=> >> media type supported (ie, LTO5, LTO4 and (read-only) LTO3).
=> >
=> > What's wrong with just defining a single media type "LTO" covering all
=> > generations in use?
=> >
=> 
=> The problem is that you may want to separate your volumes so bacula
=> does not want to try to write to an LTO2 tape on an LTO5 drive.
=> Remember that with LTO drives you can read 2 generations back but only
=> write 1 generation back.

When we moved to an LTO4 library, our solution to that issue was to update
the volume status on all the LTO-2 media to "Read-Only" (in the bacula
database, but this could have been done with the physical read-only tab
on each tape). Obviously, this would be a problem if we wanted to use
both the LTO3 and LTO4 libraries.

Thanks,

Mark

=> 
=> 
=> John
=> 
=> 
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