Re: Loopback filesystems for mail storage
On 8/17/2013 9:01 AM, Kumar Appaiah wrote:
>> 1. What is the best filesystem for Maildirs with several tens of
>> thousands of messages?
...
>> 3. What filesystem would allow quick file access? I'd like to be able
>> to view the Maildirs in Mutt, and index and search it using
>> notmuch. XFS is something searches on the interwebs revealed, but I've
>> also heard people mention Btrfs, JFS etc. If this is too long to
>> answer, I'd appreciate a pointer to a resource that I could read.
The filesystem isn't the bottleneck with maildir, the latency due to
disk head seeks is the bottleneck. XFS can help to a small degree on
mail servers with muti-user parallel access, but it won't noticeably
increase performance over EXT3/4 for a single user maildir workload, nor
will any filesystem. If you want fast access to tens of thousands of
maildir files, buy an SSD.
And of course the simple solution is to migrate to mbox. Maildir was
created for a single purpose: to eliminate file locking contention on
the traditional UNIX single mbox file. With tens of thousands of emails
this is obviously an archival workload. As such you don't have the
locking issues. Header and body searches are many times faster with
mbox than with maildir. The only operation that is significantly slower
is deleting an email. I'll assume mutt uses mmap to access mbox files,
so large file sizes shouldn't be a problem.
FWIW, I have some 100K+ emails, mostly list mail, in a couple dozen
active mbox files. Full body searching is relatively quick on a file
containing 20K emails and on a gzipped file containing 17K+ emails, even
with stale FTS indexes in both cases. These mbox mails are stored on a
Dovecot server w/dual 550MHz CPUs, 384MB RAM, with a single effective
7.2K SATA spindles--pretty old and slow hardware. mbox performance is
more than acceptable.
--
Stan
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