Redundant Mail Servers
Hi, We need to implement redundant mail servers and I'm looking for some ideas. The two mail servers are in different offices but should at all times contain identical data (well all of the same email at least). So far: - Postfix will be the MTA - Courier IMAP will be used for mail retrieval - LDAP for storing account information and as much email config as possible - Failover will require manual intervention My initial idea was to have email@primary copied to email@backup automatically in the last stages of delivery and to run a nightly rsync from the primary that would synchronize messages. This is a lot of overhead that I'd rather avoid ... particularly because of problems I've seen with rsync in the past. The two mailservers are connected by a private 100Mb link. We have also considered using DRBD or NBD in combintation with RAID1 to get a shared/mirrored filesystem. Any thoughts on this? Thanks, -- Fraser Campbell [EMAIL PROTECTED] Starnix Inc. Telephone: (905) 771-0017 ext. 223 Thornhill, Ontario, Canada http://www.starnix.com/ Professional Linux Services Products -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of unsubscribe. Trouble? Contact [EMAIL PROTECTED]
Redundant Mail Servers
Hi, We need to implement redundant mail servers and I'm looking for some ideas. The two mail servers are in different offices but should at all times contain identical data (well all of the same email at least). So far: - Postfix will be the MTA - Courier IMAP will be used for mail retrieval - LDAP for storing account information and as much email config as possible - Failover will require manual intervention My initial idea was to have [EMAIL PROTECTED] copied to [EMAIL PROTECTED] automatically in the last stages of delivery and to run a nightly rsync from the primary that would synchronize messages. This is a lot of overhead that I'd rather avoid ... particularly because of problems I've seen with rsync in the past. The two mailservers are connected by a private 100Mb link. We have also considered using DRBD or NBD in combintation with RAID1 to get a shared/mirrored filesystem. Any thoughts on this? Thanks, -- Fraser Campbell [EMAIL PROTECTED] Starnix Inc. Telephone: (905) 771-0017 ext. 223 Thornhill, Ontario, Canada http://www.starnix.com/ Professional Linux Services Products
Re: redundant mail servers
-BEGIN PGP SIGNED MESSAGE- Hash: SHA1 Hi, It is too complex. I do the following: I have a friend who knows (a little) the topology of our network. I write root and users passwords on the paper, put it into the safe, and ask my boss to call him, if something goes wrong... ;) I want to setup a redundant mail system using exim with maildirs. I thought I use two mail servers (one scsi controller each) and one scsi raid. 1.Server1 ---SCSI--- RAID5 ---SCSI--- Server2 or to remove the RAID as a Single Point of Failure: 2 RAIDs and 4 SCSI controllers: /---SCSI--- RAID5 1 ---SCSI---\ 2.Server1 Server2 \---SCSI--- RAID5 2 ---SCSI---/ In both cases mail is delivered to the users homes into maildirs, which will reside on the RAID. Is it possible (case 1) to mount one ext2 partition on two computers at the same time? Is it possible (case 2) to run a software raid1 over two partitions (one on each raid5) from both computers at the same time? Please let me know, if I'm heading in the wrong direction. The setup will be for a team with 20 persons, so there won't be too much mail traffic. The only problem is, I won't be reachable for 2 months, and therefore the system should run without the need of a sysadmin. Well, there is another one - I've only 15 days left to set it up. I also thought about using just 2 computers one harddrive each. The homes on server one are mounted as /home-remote on server 2 via nfs and vice versa. Both MTAs should deliver each mail twice (into /home and /home-remote and the pop3/imap servers serve the mails from /home). If one computer goes down, the other one would have all the mails. However I think, this becomes really nasty, when using .forward files. Any help would make me very happy. tia florian - -- Andrei. -BEGIN PGP SIGNATURE- Version: GnuPG v1.0.6 (GNU/Linux) Comment: For info see http://www.gnupg.org iD8DBQE8VumfNJ8kL/cM9QkRAtBeAJ96TlblAIRzClcG5AreqYOjeG2mqQCgtRPg LHQoIxtJoktN8PdHSr69Cow= =OQZI -END PGP SIGNATURE- -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of unsubscribe. Trouble? Contact [EMAIL PROTECTED]
Re: redundant mail servers
On Sat, 26 Jan 2002 16:38, Jeremy C. Reed wrote: On Sat, 26 Jan 2002, Florian Friesdorf wrote: Why do you need something special for only 20 users anyway? I'll be in South America for 2 months with only seldom Internet Access. They know their NT desktops, but not their servers. So I want a solution, where they can't do too much wrong and I don't have to worry while being away. Consider finding a company (or individual) that would be willing to help in an emergency. I second that. There's plenty of Linux users in every country. Finding someone who can deal with basic hardware failures while you're away should be quite easy. Finding someone who is willing and able to debug drbd and heartbeat problems will by much harder. -- http://www.coker.com.au/bonnie++/ Bonnie++ hard drive benchmark http://www.coker.com.au/postal/ Postal SMTP/POP benchmark http://www.coker.com.au/projects.html Projects I am working on http://www.coker.com.au/~russell/ My home page -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of unsubscribe. Trouble? Contact [EMAIL PROTECTED]
redundant mail servers
Hi, I want to setup a redundant mail system using exim with maildirs. I thought I use two mail servers (one scsi controller each) and one scsi raid. 1.Server1 ---SCSI--- RAID5 ---SCSI--- Server2 or to remove the RAID as a Single Point of Failure: 2 RAIDs and 4 SCSI controllers: /---SCSI--- RAID5 1 ---SCSI---\ 2.Server1 Server2 \---SCSI--- RAID5 2 ---SCSI---/ In both cases mail is delivered to the users homes into maildirs, which will reside on the RAID. Is it possible (case 1) to mount one ext2 partition on two computers at the same time? Is it possible (case 2) to run a software raid1 over two partitions (one on each raid5) from both computers at the same time? Please let me know, if I'm heading in the wrong direction. The setup will be for a team with 20 persons, so there won't be too much mail traffic. The only problem is, I won't be reachable for 2 months, and therefore the system should run without the need of a sysadmin. Well, there is another one - I've only 15 days left to set it up. I also thought about using just 2 computers one harddrive each. The homes on server one are mounted as /home-remote on server 2 via nfs and vice versa. Both MTAs should deliver each mail twice (into /home and /home-remote and the pop3/imap servers serve the mails from /home). If one computer goes down, the other one would have all the mails. However I think, this becomes really nasty, when using .forward files. Any help would make me very happy. tia florian -- Florian Friesdorf [EMAIL PROTECTED] OpenPGP key available on public key servers -- Save the future of Open Source -- - Online-Petition against Software Patents - -- http://petition.eurolinux.org --- msg04994/pgp0.pgp Description: PGP signature
Re: redundant mail servers
Florian Friesdorf said : Is it possible (case 1) to mount one ext2 partition on two computers at the same time? No. Mounting may modify the superblock, and confuse the other machine suffisently for it to crash and leave the FS in an unexpected state. Well, there is another one - I've only 15 days left to set it up. Mmmm. Good luck :-). I'm doing that kind of stuff here whith DRBD[1] and heartbeat[2]. The main difference is that we have only one server active at a given time and the data is always synchronised. If you have the cash, you can also look for a GFS or OpenGFS[3] compatible storage hardware. This is the ultimate trick to solve your problem, but it gets quite expensive... Nicolas [1] : URL:http://www.complang.tuwien.ac.at/reisner/drbd/ [2] : URL:http://www.linux-ha.org/ [3] : URL:http://www.opengfs.org/ -- [EMAIL PROTECTED] -- http://nicolas.bouthors.org/ -- +33 6 2071 6234 Administateur Systèmes et Réseaux --GHS--38, Rue du Texel -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of unsubscribe. Trouble? Contact [EMAIL PROTECTED]
Re: redundant mail servers
On Fri, Jan 25, 2002 at 03:33:04PM +0100, Nicolas Bouthors wrote: Florian Friesdorf said : Is it possible (case 1) to mount one ext2 partition on two computers at the same time? No. Mounting may modify the superblock, and confuse the other machine suffisently for it to crash and leave the FS in an unexpected state. That's a pity :-( Well, there is another one - I've only 15 days left to set it up. Mmmm. Good luck :-). Thanks a lot. But with your hints, this has become more achievable. I'm doing that kind of stuff here whith DRBD[1] and heartbeat[2]. The main difference is that we have only one server active at a given time and the data is always synchronised. I just read through the drbd homepage and HOWTO. Sounds very good to me. Can you recommend it? Did anyone experience any strange/bad behaviour using it? From what I've read, I'm going to try last stable version 0.5.8 and therefore downgrade to 2.2.x kernels (at the moment I'm running 2.4.x) If you have the cash, you can also look for a GFS or OpenGFS[3] compatible storage hardware. This is the ultimate trick to solve your problem, but it gets quite expensive... Mmmm - Well, I think I'll try drbd. thx florian -- Florian Friesdorf [EMAIL PROTECTED] OpenPGP key available on public key servers -- Save the future of Open Source -- - Online-Petition against Software Patents - -- http://petition.eurolinux.org --- msg04997/pgp0.pgp Description: PGP signature
Re: redundant mail servers
Hi On Fri, Jan 25, 2002 at 03:14:18PM +0100, Florian Friesdorf wrote: Hi, I want to setup a redundant mail system using exim with maildirs. I thought I use two mail servers (one scsi controller each) and one scsi raid. 1.Server1 ---SCSI--- RAID5 ---SCSI--- Server2 [snip] Is it possible (case 1) to mount one ext2 partition on two computers at the same time? As Nicolas said you can't do that with ext2, but you can with OpenGFS. OpenGFS is still in development, though, so I don't know how stable it is. I have not used it. You wouldn't be able to use RAID from both machines, though, so it would have to be something like this: Server1--[SCSI]--[disk with OpenGFS]--[SCSI]--Server2 Of course, if your disk dies you have no data... Is it possible (case 2) to run a software raid1 over two partitions (one on each raid5) from both computers at the same time? As far as I know, no. Linux software RAID was not designed to be accessed from more than one machine. hmmm... maybe you could do it with hardware RAID. I hope that helps. -- Michael Wood [EMAIL PROTECTED] -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of unsubscribe. Trouble? Contact [EMAIL PROTECTED]
Re: redundant mail servers
Florian Friesdorf said : I just read through the drbd homepage and HOWTO. Sounds very good to me. Can you recommend it? Did anyone experience any strange/bad behaviour using it? Well I do. Here we have a failover 2-node cluster serving NFS over DRBD and (surprisingly) it works like a charm. I guess it would be no major hassle to setup a mailserver in the same fashion... A few caveats though : - Use a dedicated ethernet link for replication - Imagine and plan every possible failure cases and create a backup plan for each. From what I've read, I'm going to try last stable version 0.5.8 and therefore downgrade to 2.2.x kernels (at the moment I'm running 2.4.x) I'm using 0.58 here (because we *had* to use 2.2), and it works, but Phillip Reisner (DRBD's Author) strongly suggest upgrading. And I believe he's right. Whith 0.58 you might have very weird problems if the sync link goes down. It is said that 0.6.* are better... Didn't check. Nicolas -- [EMAIL PROTECTED] -- http://nicolas.bouthors.org/ -- +33 6 2071 6234 Administateur Systèmes et Réseaux --GHS--38, Rue du Texel -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of unsubscribe. Trouble? Contact [EMAIL PROTECTED]
Re: redundant mail servers
On Sat, 26 Jan 2002 01:14, Florian Friesdorf wrote: Is it possible (case 2) to run a software raid1 over two partitions (one on each raid5) from both computers at the same time? It's not possible to have one partition in use by two computers at the same time unless you use GFS or something similar. Please let me know, if I'm heading in the wrong direction. The setup will be for a team with 20 persons, so there won't be too much mail traffic. The only problem is, I won't be reachable for 2 months, and therefore the system should run without the need of a sysadmin. Well, there is another one - I've only 15 days left to set it up. With only 15 days you don't want something that will take a long time to setup. Also you don't want something overly complex, the more complex the more likely it is to break. I suggest having a single machine with RAID-1. Then entire categories of potential problems such as issues of accidentally mounting the same filesystem on both machines will just disappear. Why do you need something special for only 20 users anyway? -- http://www.coker.com.au/bonnie++/ Bonnie++ hard drive benchmark http://www.coker.com.au/postal/ Postal SMTP/POP benchmark http://www.coker.com.au/projects.html Projects I am working on http://www.coker.com.au/~russell/ My home page -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of unsubscribe. Trouble? Contact [EMAIL PROTECTED]
Re: redundant mail servers
On Sat, Jan 26, 2002 at 01:28:39PM +1100, Russell Coker wrote: On Sat, 26 Jan 2002 01:14, Florian Friesdorf wrote: Please let me know, if I'm heading in the wrong direction. The setup will be for a team with 20 persons, so there won't be too much mail traffic. The only problem is, I won't be reachable for 2 months, and therefore the system should run without the need of a sysadmin. Well, there is another one - I've only 15 days left to set it up. With only 15 days you don't want something that will take a long time to setup. Also you don't want something overly complex, the more complex the more likely it is to break. That's what I think, too. I suggest having a single machine with RAID-1. Then entire categories of potential problems such as issues of accidentally mounting the same filesystem on both machines will just disappear. Why do you need something special for only 20 users anyway? I'll be in South America for 2 months with only seldom Internet Access. They know their NT desktops, but not their servers. So I want a solution, where they can't do too much wrong and I don't have to worry while being away. I'm now trying heartbeat and drbd as supposed by Nicolas Bouthors. On the other hand, in the past 3 years, we had only one hardware failure (overheated cpu, due to damaged fan), and it's only 2 months... Perhaps I should leave everything as it is. ;-) -- Florian Friesdorf [EMAIL PROTECTED] OpenPGP key available on public key servers -- Save the future of Open Source -- - Online-Petition against Software Patents - -- http://petition.eurolinux.org --- msg05012/pgp0.pgp Description: PGP signature
