Mailbox cluster with Cyrus Murder

The central mailbox server mail.tu-chemnitz.de is realised by a distributed mailbox cluster. Two backend servers manage the e-mails, which are stored in the storage system. Access is provided by two frontend servers, which authenticate user access and then switch through to the respective backend server depending on the mailbox queried. The assignment of mail folders to backend servers is managed by a so-called MUPDATE server. The acceptance of sent e-mails and the mail delivery is done via the MTA servers. The individual servers are addressed by users via the name mail.tu-chemnitz.de. The redundant components are switched by a layer 4 switch (Netscaler).

The system is scalable, i.e. more servers can be added at any time if necessary, with nothing changing for users.

All servers of our "Cyrus Murder Cluster" are operated under the Linux operating system with the Cyrus-imapd software. As SMTP server we use Exim, which is also developed as open source software.

Mailbox server: Technology (and history)

since November 2020: Consolidation, separation of MTA servers (SMTP)

• unique name mail.tu-chemnitz.de for IMAP, POP3, SMTP and HTTPS (Webmail) via Netscaler (Layer-4-switch)
• virtual servers – 2 backends, 2 frontends, MUPDATE server on a frontend, 2 MTA servers (delivery by LMTP), TUCSAN storage
• System: Linux 3.10.X, Scientific Linux 7, xfs
• Software: Cyrus-imapd 2.4.X, Exim 4.X, authentication SASL + PAM + Kerberos 5/GSSAPI

December 2012: Update (pat / postman)

• virtual servers – up to 5 backends, 2 frontends, MUPDATE server on a frontend, TUCSAN storage
• System: Linux 2.6.X, Scientific Linux 6, ext4 + xfs
• Software: Cyrus-imapd 2.4.X, Exim 4.X, authentication SASL + PAM + Kerberos 5/GSSAPI

April 2012

• secured protocola only – IMAP/POP3 via STARTTLS or IMAPS/POP3S

2010 – usage of virtual servers

March 2007 – Mailbox cluster with Cyrus Murder (pat)

• Hardware: 2 backend servers, 1 frontend server, 1 MUPDATE server, TUCSAN storage
• System: Linux 2.6.X, Scientific Linux 4, ext3 + xfs
• Software: Cyrus-imapd 2.3.X, Exim 4.X, authentication SASL + PAM + Kerberos 5/GSSAPI

January 2006:

• Hardware: identical, RAID since 06/2005 about 1 TB
• System: Linux 2.6.X, Scientific Linux 4, ext3 + xfs
• Software: Cyrus-imapd 2.3.X, Exim 4.X, authentication SASL + PAM + Kerberos 5/GSSAPI, without Kimberlite

June 2003: 3rd server (hedwig / errol)

• redundant with Kimberlite cluster
• Hardware: 2 computers, each 2 x AMD Athlon, 1,8 GHz, 3 GB RAM, 1 RAID system ca. 440 GB
• System: Linux 2.4.X, Redhat 7.3, ext3 FS
• Software: Cyrus-imapd 2.1.X, Exim 4.X, authentication SASL + PAM, Kimberlite cluster

February 2001: 2nd Server (pat)

• Hardware: AMD Athlon, 1 GHz, 1 GB RAM, 2 x 70 GB EIDE internal
• System: Linux 2.2.X, Redhat 6.2, ext2 FS
• Software: Cyrus-imapd 2.0.X, Exim 3.X, authentication SASL + PAM
• IDE-disks accelerated (hdparms), enhanced file descriptors
• Problems: disk failures, corrupt Cyrus DB

December 1999: 1st mailbox server (postman) based on Cyrus-imapd

• Hardware: Intel Pentium III, 450 Mhz, 512 MB RAM, 80 GB Arena RAID extern
• System: Linux 2.2.X, Redhat 6.2
• Software: Cyrus-imapd 1.6.X, Sendmail 8.10.X, stunnel, authentication SASL + PAM
• Probleme: RAID failures …

Before:

• Hardware: Sparc 10, 128 MB RAM, 2,9 GB Disk
• System: Solaris 2.6
• Software: sendmail, NFS, ipop3d, imapd (UW), (stunnel)