Hi guys I'm about to embark on a project replacing a legacy single mail server running proprietary software with a cluster of Dovecot servers. We clearly need a shared mail store for these servers, but we are not happy with simply using a server running NFS as this becomes a single point of failure. What have other people used? AFAICT our options are: * A shared block device (Fibre Channel, iSCSI, ATAoE etc) running GFS or similar to allow multiple servers to access it concurrently * Two or more NFS units, either with built-in support for replication of FS changes and failover, or with scripts for achieving this functionality I prefer option 1, although it's expensive. What have other people used? Do we have other options? TIA -- Jasper Bryant-Greene Director Album Limited jasper at albumltd.co.nz +64 21 708 334 / 0800 425 286 http://www.albumltd.co.nz/
Jasper Bryant-Greene wrote:> Hi guys > > I'm about to embark on a project replacing a legacy single mail server > running proprietary software with a cluster of Dovecot servers. We > clearly need a shared mail store for these servers, but we are nothappy> with simply using a server running NFS as this becomes a single pointof> failure. > > What have other people used? AFAICT our options are: > > * A shared block device (Fibre Channel, iSCSI, ATAoE etc)running> GFS > or similar to allow multiple servers to access it concurrently > > * Two or more NFS units, either with built-in support for > replication > of FS changes and failover, or with scripts for achieving this > functionality > > I prefer option 1, although it's expensive. What have other peopleused?> Do we have other options?I recommend a pair of NetApp filers (e.g. 2 x 3020c) exporting NFS from shared disk shelves in their high-availability mode. This is a hybrid of the two options, except a) it's a fully supported and stable NetApp configuration, b) they're sharing disk storage, c) you're not hog-tied to GFS, d) it's the best NFS implementation in the world (you can even trust the fcntl locking), e) it's really fast, f) NetApp's onboard snapshots and other funky software bits will make you wonder how you lived without them, g) the HA actually works. I have a six-digit userbase with mailboxes in this configuration. JG
dovecot at redigloo.org wrote:> My ears prick up whenever I hear mention of NetApps and Dovecot. > > Which operating system (Linux, Solaris, Solaris x86...) are you > running.The NFS clients w/Dovecot are currently running Linux 2.6.16 with Trond Myklebust's Linux-2.6.16-NFS_ALL.dif applied (see http://client.linux-nfs.org/). This combo has been stable for months. And yes, we use fcntl locking, and mount noac,actimeo=0. JG
Jasper Bryant-Greene writes:> I prefer option 1, although it's expensive. What have other people used? > Do we have other options?How redudant does it need to be? How big is the setup? Does whatever OS you plan to use, works well with NFS? I use FreeBSD as the OS and we had terrible experience with NFS. I think NFS servers are probably the way to go... if you have the budget, but that was not an option for us. We are planning on having a backup/spare server and doign RSYNCS to it, but that may not be acceptable if you don't the possibility of loosing any mail.