Re: [Dovecot] Best Cluster Storage
On Mon, Jan 17, 2011 at 7:32 AM, Jan-Frode Myklebust janfr...@tanso.net wrote: On Fri, Jan 14, 2011 at 05:16:50PM -0800, Brad Davidson wrote: Don't give up on the simplest solution too easily - lots of us run NFS with quite large installs. As a matter of fact, I think all of the large installs run NFS; hence the need for the Director in 2.0. Not all, if this counts as large: Filesystem Size Used Avail Use% Mounted on /dev/gpfsmail 9.9T 8.7T 1.2T 88% /maildirs Filesystem Inodes IUsed IFree IUse% Mounted on /dev/gpfsmail 105279488 90286634 14992854 86% /maildirs how do you backup that data? :) -ah
Re: [Dovecot] GlusterFs - Any new progress reports?
Anyone had success using some other clustered/HA filestore with dovecot who can share their experience? (OCFS/GFS over DRBD, etc?) My interest is more in bootstrapping a more highly available system from lower quality (commodity) components than very high end use we use drbd with ext3 in a active/passive setup for more than 1 mailboxes. works like a charm! I'm not really trusting cluster filesystems and most cluster filesystems are not made for small files. Alex
Re: [Dovecot] quick question
I think mail is the wrong application for nfs, because nfs is slow for metadata operations. Would rather use it for vm hosting than mail. We used to have a small clustered netapp with 10k hdds and three frontend servers with postfix and courier imap/pop3. the setup was stable however the performance was not good. So we build a imap cluster out of a pair of dell r710 (6 x 15K hdds) with centos 5 drbd and heartbeat. I will scale this setup by adding another pair of r710 servers and randomizing the mailboxes between the imap/pop3 cluster pairs. An imap proxy will direct the users to the right server and the frontend mx servers will also send the mail to the right server by using smtp as tranport and postfix transport maps for routing. In the future i would like to switch from courier to dovecot and using lmtp as transport to our mailstore. We currently have 1 mailboxes only 300 - 400 imap connections but a lot pop access the load an the active r710 is only 0.10 :) I think mail is a problem which you can easily partition so why have all eggs in one basket :) alex
Re: [Dovecot] Anyone successfully setup Continous Backup of mailboxes using rsync ?
i use drbd to keep the mailstore redundant and rsnapshot for backup.
Re: [Dovecot] Recommended method?
Now I am thinking of taking that same thinking and getting rid of the deliver over nfs and deliver directly to the raid server like you said. We have such a setup. 3 MX servers running postfix and antispam software. 2 clustered (drbd, heartbeat) IMAP/POP3 Servers The 3 MX server deliver via smtp to the imap cluster and there runs another postfix instance without spamchecks. Keep in mind your alias setup - our mx servers expand the aliases before they deliver to the backend postfix. Be sure to disable the aliases on the backend mta otherwise you will get your mails twice. normally the backend mta should not send any mail but if there are problems with the quota it should reach the sender, therefore we have enabled the aliases only for outgoing mail. this helps in the special case if an internal users sends to another internal user which is over quota and the senders address is an alias :)
Re: [Dovecot] [OT] DRBD
On Mon, Nov 23, 2009 at 10:25 PM, Rodolfo Gonzalez Gonzalez rgonza...@gnt.cc wrote: Hello all, has someone worked with DRBD (http://www.drbd.org) for HA of mail storage? if so, does it have stability issues? comments and experiences are thanked :) Thanks, Rodolfo. We have deployed active/passive DRBD Mailserver for a customer with ~ 5000 mailboxes. runs nice without any problems. CentOS 5.3 Heartbeat 1 ! DRBD 8.3.x LVM If you try to use LVM/ext3 with DRBD and you want to use consistend snapshots, use this setup http://www.drbd.org/users-guide-emb/s-lvm-drbd-as-pv.html Storage layer: disks/hwraid/softwareraid - drbd - LVM - fs this way lvm can trigger the fs with a freezecall before the blocklevel snapshot. We currently migrate our 1 Mailcluster from a netapp storage to multiple storage server with drbd. Our other project the webcluster runs with about 1000 sites (Typo3/Joomla) on a CentOS nfs-server backed with the drbd. The failover time is about 4 seconds and no pending write ist lost.
Re: [Dovecot] Dovecot and SATA Backend
Extra question, what is the better : iSCSI SATA backend or NFS share ? NFS share is more convenient to have a failover server. Everyone wants to use nfs for mailstorage, because it is convenient, but nfs is the wrong storage model for mail. NFS shines on big files but metadata performance is low, too much overhead! We currently have a mailcluster with 1 mailboxes and the data ist stored on a netapp storage. If you have a Mailbox with more then 1000 mails, it gets slow over nfs. Our new architecuture will look like this: No NFS, no iSCSI we use DAS. There will be multiple dedicated mailbox server in pairs with a small postfix instance and dovecot. These Servers will only be used for delivering/IMAP/POP3. To get HA we use DRBD und Heartbeat in active/passive setup. In the front there will be a IMAP/POP3 proxy to direct the user to his mailbox server. This setup scales and is cheap, you only have to find a way to distribute the mailboxes around all mailbox servers. I think rackspace email uses a similar setup with drbd and dovecot.
Re: [Dovecot] Dovecot and SATA Backend
But faster is not always the way to measure things. In this topic, I think that raw disk access speed is not a critical value; I've tested our setup with maildir on NFS and performance is close enough to local disks. Given this, I prefer the extra features our NAS/SAN setup gives us, like having data replication between phisically separated disks in a couple of clicks ,redundant paths to data, easier management, ... In my test local storage was always ~ 2 times faster than nfs. if you have the deep pockets to buy all the storage gear and replication licenses/maintainence then it's for sure far better. But if you are an isp, you have to sell the storagespace for pennies. So we came up with a cheap robust and scalable storage solution special to our mailsetup. It Supports HA with blocklevel-replication and snapshots with lvm so it's even some what manageable. Another point against nfs is that i wanted to avoid potential locking/coruption problems. I know it can be solved by always redirecting the same user to the same server, but then again i loose the convenience of nfs. So i ditch nfs complety and use multiple storage servers in pairs running dovecot.
