Re: Store FS related questions

[Marcus Brinkmann]

On Tue, Jan 15, 2002 at 05:41:41PM -0800, Galchin Vasili wrote:
>      1) In "store.h" type servers, what is the best way for me to
>             understand the pager.c file? I.e. is it external storage
>             management?

It is external memory management, eg the callbacks required by libpager.
Mapped memory is implemented on top of that external memory management.
To understand libpager, you need to understand external memory management in
Mach (see gnumach/doc/mach.texi).
 
>     2) A brief answer to what is defpager server and where are the
>            other pieces like main.c?

See mach-defpager/.  The default pager is exactly that: The default pager
registered with the Mach kernel.  Eg the support for paging
partitions/files.

>     3) Using kids (children), is it possible to have "kids" that
>             all have RAID5 semantics  and the parent which
>             implements striping across all
>             kids/children as a collection??

I don't know RAID5.  We have RAID-0(2) support.  In general, you can combine
all store types in any logical way.

>     4) Assume children in 3), is it possible to have a parent
>           store with gunzip semantics across all children?

If you use gunzip:STORE where store is any store, it will create an
uncompressed copy in memory.  STORE can also be the concat store, or ileave
store or whatever.  But note that this is probably not what you want (writes
gets lost, the whole store will be kept uncompressed in memory) if you want
transparent disk compression.  For this, a new store class has to be written
(and probably some other algorithm than gzip has to be used).

>     5) Function file_get_storage_info - where is it?

This has to be implemented by the respective server/translator/filesystem.
Try grep -r.  For example, in ext2fs/storeinfo.c

Thanks,
Marcus

-- 
`Rhubarb is no Egyptian god.' Debian http://www.debian.org brinkmd@debian.org
Marcus Brinkmann              GNU    http://www.gnu.org    marcus@gnu.org
Marcus.Brinkmann@ruhr-uni-bochum.de
http://www.marcus-brinkmann.de