My project wish-list for the next 12 months
Kamal R. Prasad
kamalp at acm.org
Thu Dec 2 10:03:01 PST 2004
Andre Oppermann wrote:
> Sam wrote:
>
>> On Thu, 2 Dec 2004, Andre Oppermann wrote:
>>
>>> Scott Long wrote:
>>>
>>>> 5. Clustered FS support. SANs are all the rage these days, and
>>>> clustered filesystems that allow data to be distributed across many
>>>> storage enpoints and accessed concurrently through the SAN are very
>>>> powerful. RedHat recently bought Sistina and re-opened the GFS source
>>>> code, so exploring this would be very interesting.
>>>
>>>
>>> There are certain steps that can be be taken one at a time. For
>>> example
>>> it should be relatively easy to mount snapshots (ro) from more than one
>>> machine. Next step would be to mount a full 'rw' filesystem as 'ro' on
>>> other boxes. This would require cache and sector invalidation
>>> broadcasting
>>> from the 'rw' box to the 'ro' mounts. The holy grail of course is
>>> to mount
>>> the same filesystem 'rw' on more than one box, preferrably more than
>>> two.
>>> This requires some more involved synchronization and locking on top
>>> of the
>>> cache invalidation. And make sure that the multi-'rw' cluster stays
>>> alive
>>> if one of the participants freezes and doesn't respond anymore.
>>>
>>> Scrolling through the UFS/FFS code I think the first one is 2-3 days of
>>> work. The second 2-4 weeks and the third 2-3 month to get it right.
>>> If someone would throw up the money...
>>
>>
>> You might also design in consideration for data redundancy. Right now
>> GFS largely relies on the SAN box to export already redundant RAID
>> disks. GFS sits on a "cluster aware" lvm layer that is supposed to
>> be able to do mirroring and striping, but I'm told it's not
>> stable enough for "production" use.
>
>
> Data redundancy would require a UFS/FFS redesign. I'm 'only' talking
> about enhancing UFS/FFS but keeping anything ondisk the same (plus
> some more elements).
>
If you add redundancy code into UFS/FFS, that will slow down its
performance (even for those not seeking redundancy).
A better way would be to have another filesystem implementation like
VxFS (veritas filesystem). Im not sure if they have published papers/put
their techniques into public domain.
regards
-kamal
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