Re: VSS: Possible to make a transportable shadow copy of a raw disk?

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They are admittedly small, and that is likely our fallback position. Main one is
portability -- you can move your LUN to a host that is running on a different, non-Windows
platform and our OS will see the database natively. The next biggest one is ensuring that
all the SCSI pass through stuff will work with a file handle, or will we have to maintain
both a handle to the physicaldrive and a handle to the pseudo-disk file?

--
Tom

"Alexander Grigoriev" <alegr@xxxxxxxxxxxxx> wrote in message
news:u4sEzQs6FHA.1720@xxxxxxxxxxxxxxxxxxxxxxx
> What are advantages of using raw FS vs non-buffered random access to a pre-allocated big
> file? Other than not having to pass through one level of driver stack?
>
> "Tom Stewart" <tastewar@xxxxxxxxxxxxxxxx> wrote in message
> news:ekVXKfr6FHA.3340@xxxxxxxxxxxxxxxxxxxxxxx
>> Hi Rhett-
>>
>> I see that you remember me -- don't know if that works to my advantage or disadvantage
>> :-)
>>
>> Your understanding is basically correct. By "raw" I mean that it has no file system
>> recognized by Windows. We can avoid writing to sector 0, so that Windows can write a MBR
>> with an empty partition table and a signature. This makes Windows recognize the disk as
>> Basic but unallocated. If it would help, we can probably even create a partition table
>> entry that would essentially reserve the entire disk, but with an unrecognizable (except
>> to us) file system type. That's as far as we can go easily.
>>
>> You say, "VSS backup is based on windows filesystem" but VSS is only an intermediary, not
>> a backup application. The backup requestors (VSS terminology) we work with are perfectly
>> capable of doing raw disk backup (i.e. sector-by-sector). The hardware providers we're
>> dealing with are perfectly capable of doing LUN based snaps or mirrors. In fact, the
>> hardware providers in reality can *only* do LUN based shadows -- they don't know or care
>> about filesystems.
>>
>> We've done our own VSS-style SAN based backups for years now, where we've isolated the
>> hardware specific code to platform specific dll's, and we've got a vendor agnostic
>> protocol for communication to the backup applications. We're just hoping to be able to
>> adopt VSS going forward, because it is essentially the framework we were looking for
>> years ago when we wrote our current solution.
>>
>> In addition, I know that both db2 and Oracle support raw disk devices for their
>> databases, and at least Oracle had announced that they'd be writing a VSS Writer (at
>> TechEd 2004, according to Keith Hagerman [1]).
>>
>> So, what I'm trying to get a definitive answer to, is whether VSS is going to act as this
>> intermediary, or is it going to get in the way -- making something which is very possible
>> today (creating snaps/mirrors of LUNs and backing them up) impossible. It would seem a
>> shame, because there's no reason not to support it, except that perhaps nobody thought to
>> include a way to add a path like, \\.\PhysicalDrive3 to a component. But I need a
>> *definitive* answer. And assuming it's possible, how to specify a physical drive path as
>> a component.
>>
>> Thanks, Rhett.
>>
>> --
>> Tom
>>
>> [1] http://groups.google.com/group/microsoft.public.storage/msg/59f89922adb68d13
>>
>>
>> "Rhett Gong [MSFT]" <v-raygon@xxxxxxxxxxxxxxxxxxxx> wrote in message
>> news:csd%23aSn6FHA.1236@xxxxxxxxxxxxxxxxxxxxxxxx
>>> Hello Tom,
>>> Glad to see you again.
>>>
>>> Based on my understanding, you would like to use VSS API to make more efficient backup
>>> for your database. If it is database,
>>> I would suggest you use VSS_CT_DATABASE as the component type. I am not sure what a RAW
>>> disk, but if you mean
>>> something like unformatted disks, I do not think VSS can works for you. So far as I
>>> know, VSS backup is based on windows
>>> filesystem and is only supported on Microsoft Windows Server 2003 and Microsoft Windows
>>> XP currently.
>>>
>>> Thanks,
>>> Rhett Gong [MSFT]
>>> Microsoft Online Partner Support
>>> Get Secure! - www.microsoft.com/security
>>> http://support.microsoft.com/default.aspx?scid=/servicedesks/msdn/nospam.asp&SD=msdn
>>>
>>> This posting is provided "AS IS" with no warranties and confers no rights.
>>>
>>
>>
>
>


.

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