[Kde-pim] Akonadi(Next): Thoughts on caching

[Martin Steigerwald]

Hi!

Considering:

[Akonadi] [Bug 338402] File system cache is inneficient : too many file per 
directory

Bug 332013 - NFS with NetApp FAS: please split payload files in file_db_data
into several directories to avoid reaching maxdirsize limit on Ontap / WAFL
filesystem

Bug 341884 - dozens of duplicate mails in ~/.local/share/akonadi/file_db_data

and maybe others, I wonder about caching:


Surely caching 7 GB of an IMAP account that according to Outlook Web Access 
has 38,4 GiB (I doubt it has that much, I don´t know how Exchange accounts 
space, it surely didn´t have that much space on Zimbra), without the user 
having request offline access, seems over the top to me. Especially when thats 
done in about 500000+ files in a single file_db_data directory on the local 
disk.

But now I told KMail to download all messages for offline use (former 
disconnected IMAP functionaliy), cause I thought, if it already caches 7 GiB 
of my IMAP account anyway, I don´t bother over the few additional GiB it may 
add for full caching (I still don´t think that 38,4 GiB is just for the mails, 
maybe it includes space usage for full text indexing). And this had the 
interesting effect that now it seems I can actually use KMail with Exchange 
at least a bit better. Its still not good when Exchange drops IMAP connections 
or delays request answers, Akonadi can still not cope well with that up to the 
point KMail does *nothing* anymore, until I restart either KMail and/or 
Akonadi (sometimes it seems to need both).


So I think there are two needs for caching:

1) Fast IMAP server (Dovecot!), fast network: Cache way less mails than what 
Akonadi caches currently in file_db_data. Maybe even do not cache all metadata, 
but well, if its fast and done once, I won´t bother.

2) Crappy IMAP server (Exchange) or slow network or slow I/O on server: Cache 
all for offline usage.

What do you think?


Trojitá has similar setting between fast, flatrate and expensive network.

I think some way to adjust the behavior for a balance between situation 1 and 
2 does make sense. Icedove has this as well. You can speficy how many days and 
the maximum size of a message to download.

Ciao,
-- 
Martin 'Helios' Steigerwald - http://www.Lichtvoll.de
GPG: 03B0 0D6C 0040 0710 4AFA  B82F 991B EAAC A599 84C7
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