[Info-vax] New filesystem mentioned

[VAXman- at SendSpamHere.ORG]

In article <qbfet7$1veo$2 at gioia.aioe.org>, =?UTF-8?Q?Arne_Vajh=c3=b8j?= <arne at vajhoej.dk> writes:
>On 5/13/2019 9:56 PM, Dave Froble wrote:
>> On 5/13/2019 8:52 PM, Arne Vajhøj wrote:
>>> On 5/13/2019 8:30 PM, Dave Froble wrote:
>>>> On 5/13/2019 6:53 PM, Arne Vajhøj wrote:
>>>>> On 5/13/2019 5:37 PM, Dave Froble wrote:
>>>>>> On 5/13/2019 2:36 PM, Michael Moroney wrote:
>>>>>>> Simon Clubley <clubley at remove_me.eisner.decus.org-Earth.UFP> writes:
>>>>>>>> There's a reason (multiple reasons actually) why so many operating
>>>>>>>> systems now support ZFS.
>>>>>>>
>>>>>>>> Unfortunately, VMS isn't likely to be one of them, given the lack
>>>>>>>> of support in VMS for modular plugin filesystems. That means adding
>>>>>>>> ZFS to VMS would be a major job.
>>>>>>>
>>>>>>> If I recall, A mentioned that ZFS and other file systems lacked the
>>>>>>> cluster support
>>>>>>> needed for clusterwide operation that VMS needs, and would require
>>>>>>> mega rototilling
>>>>>>> to add it. I don't know the details.
>>>>>>>
>>>>>>
>>>>>> An interesting statement.
>>>>>>
>>>>>> I'm wondering what would be required in the filesystem to support VMS
>>>>>> clustering?
>>>>>>
>>>>>> Not that I'm an expert on VMS clusters, but it has been my impression
>>>>>> that the OS did all the work.  But what do I know?
>>>>>
>>>>> The answer must depend a lot on what is meant by "file system".
>>>>>
>>>>> I do not think there is anything in the on disk bytes that
>>>>> are relevant for clustering.
>>>>>
>>>>> The code that does the physical transfer of data between
>>>>> disk and memory should not have anything relevant for
>>>>> clustering.
>>>>>
>>>>> But there are some higher level code that need cluster
>>>>> awareness. At least code that checks if a file being
>>>>> opened is already in use on another node. And much more
>>>>> to support effective locking of records and byte ranges
>>>>> in cluster environment.
>>>>
>>>> The DLM is cluster aware, and any locks are respected over the entire
>>>> cluster.
>>>>
>>>> For file system locks, the top level locks might be on the filespec,
>>>> which includes device.  As I may have mentioned, I'm not very
>>>> knowledgeable about VMS clusters.  Someone who knows more can add some
>>>> details.  I believe every "disk" in a cluster has a unique name.  So
>>>> the resource lock on that device and filespec should be respected and
>>>> unique throughout the entire cluster.
>>>>
>>>> The sublocks are for record numbers in the file, and would be
>>>> respected throughout the cluster.
>>>>
>>>> I believe it's just that simple.
>>>>
>>>> Now, the "stuff" that makes the DLM work across the VMS cluster, that
>>>> may be rather complex, but, it's already in there.  There are things
>>>> such as moving the locks to the node with the most usage, and such.
>>>> Really a nice tool, and from the early 1980s.  I used it for my
>>>> database product developed in 1984.  Still working.
>>>
>>> Yes.
>>>
>>> But now you are assuming that ZFS is just an ODS-something format and
>>> that RMS, SYS$QIO(W) etc. just runs on top of it.
>> 
>> So far, I don't see any problems with such assumptions.
>
>If you read the links about ZFS that I posted then it seems that
>ZFS is a lot more.
>
>> RMS is just data, whether it's internal data, or user data.  It gets 
>> stored on "disk blocks".
>> 
>> I'd assume (bad habit) that if any file system was implemented on VMS, 
>> that QIOs would be the method for access.  Now, QIO may need to know 
>> some new things.
>> 
>> For any file system to be implemented on VMS, it's going to have to work 
>> as other file systems, else what's the use?  If low level code and all 
>> new file accessing is required, the usefulness becomes much less.  Might 
>> as well go back to physical I/O.  The purpose of a file system is to be 
>> a lower level tool transparent to user code.
>
>To user code: yes.
>
>But there is a lot between the SYS$QIO(W) and RMS API's and the plates.
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What he said!

However, if RMS can say "I need block 'n' or blocks 'n through n+x'" and get
that data it should be relatively moot.  The issue will be, will the present
concept of RFA still be/remain valid.

-- 
VAXman- A Bored Certified VMS Kernel Mode Hacker    VAXman(at)TMESIS(dot)ORG

I speak to machines with the voice of humanity.