Dear List, nice to meet you :)
First post, straight to the point:
I'm wrestling from few weeks with a problem: roundcube (a webmail client) takes
too long to open a dovecot (pop/imap server) mailbox with many emails (files).
So, when such user has more than 10K emails, it takes around 1 minute to open
the mailbox.
Meanwhile, I/O %util goes to 100% and bottlenecks the whole system.
I've tried memcache(d) integration with roundcube but it doesn't eliminate the
problem.
OS is Debian Wheezy 32-bit, 16GB of ECC RAM and storage is a simple hardware
raid-1 with a couple of sata2 hard disks.
I've just used mkfs.xfs (with no tuning) and no options while mounting (in
fstab).
It looks like the problem is the slow access to dentries and inodes, so I've
set vfs_cache_pressure to 1,
forced buffering with few "find /var/mail > /dev/null"
and have it running like this from around 4 days.
Didn't help: slabs still gets flushed and opening folders is slow as before.
Current slabtop usage shows:
235352K used by xfs_inode
and
49708K used by dentry
while I would expect to have at least 1 GB of xfs_inode and at least 200MB of
dentry.
So I'm asking you:
1. is there a way to force dentries and inodes to stay in ram ?
2. can I perhaps move dentries and inodes to a dedicated SSD ?
I'm open to all possibilities, perhaps increase RAM ?
Upgrade to Debian Jessie and 64 bit ?
Let me know if I can provide more info.
Thank you very much!
Mike
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