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List:       kde-bugs-dist
Subject:    [Akonadi] [Bug 338402] File system cache is inneficient : too many file per directory
From:       Martin Steigerwald <ms () teamix ! de>
Date:       2015-01-21 9:26:05
Message-ID: bug-338402-17878-ZuagmcoPpd () http ! bugs ! kde ! org/
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https://bugs.kde.org/show_bug.cgi?id=338402

--- Comment #5 from Martin Steigerwald <ms@teamix.de> ---
Dan, I agree that lookup of an individual file will be fast with Ext4, BTRFS,
XFS, yet it causes other issues:

- updatedb
- backup: my rsync based backup to eSATA 2 TB harddisk takes way more than one
hour now. It was much quicker at some time. It maybe have also different
reasons, but my bet that the large file_db_data directories contribute to that.
It may likely be way faster with btrfs send/receive, but there are a lot of
backup solutions out there, which may have issues with a folder like this.
- any disk usage calculator like filelight will have delays on it (I showed the
5 minute time for du -sch, admitted, this has ecryptfs in between, that visibly
seems to make the performance worse)
- so add ecryptfs to the list, I did a du -sch over the uncrypted version and
it is way faster than the 5 minutes.
- or maybe NFS based setups as well
- and storage appliances with limits

Its not just Akonadi living alone with a superfast PCIe M2 SSD.

And whats about Akonadi on Windows? I bet NTFS may cope, but do you know? Or
Mac OS X with HFS+, how about that?


So arguing modern Linux filesystem can handle these amounts of files is like
arguing:

Ey, we have 16 GiB of RAM available, so why don īt reserve and use it all, even
if we do not need it.

So what is the rationale for caching that much? What is the actual benefit it
provides. I fail to see it.

I will now set that account to offline caching on my laptop. Maybe then I will
see some use. And as it already insists on keeping 7 GiB of my IMAP account
stored locally, I don īt bother if it also downloads the rest of it.

According to filelight file_db_data is the largest folder! Not even Baloo īs
email index is that large. It has just 5,3 GiB. And this one actual provides a
benefit. A huge one. And it has it in way less files.

That said, I know found that Icedove, which I used at some time also has 4,2
GiB locally. But I instructed it to keep mails for offline usage, when I
remember correctly.

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