synchronization/backup mx

[Simon Matter]

> Torsten Schlabach wrote:
>> > The config you would need is to use drbd to mirror the data
>> > directories
>>
>> Is this officially supported / endorsed?
> Not that I know of but someone else may have a better idea than me
>> I learned that Cyrus IMAPd (for whatever reason) is quite picky on
>> filesystems. From the FAQ:
>>
>> --- SNIP ---
>>
>> # Using NFS We don't recommend it. If you want to do it, it may
>> possibly work but you may also lose your email or have corrupted
>> cyrus.* files. You can look at the mailing list archives for more
>> information.
>> # Using AFS/Coda We don't recommend it. It's even less likely to work
>> than NFS. If you want to do it, it may possibly work but you may also
>> lose your email or have corrupted cyrus.* files. CMU's previous e-mail
>> system, AMS, leveraged AFS extensively for storage (and transit)
>> purposes. For various reasons it didn't scale particularly well and
>> led to CMU's interest in IMAP.
>>
>> Cyrus was designed to use a local filesystem with Unix semantics and a
>> working mmap()/write() combination. AFS doesn't provide these
>> semantics so won't work correctly.
>>
>> --- SNIP ----
> drbd isn't a file system it works on the disk level so you can have
> whatever file system on top of it. You end up with the mirrored disk
> partitions on each server being identical. AFAIK it is fully posix
> compliant and shouldn't have any of the problems mentioned above.
>> The concept of mirroring the BerkeleyDB database files on a filesystem
>> level does not sound that reliable to me. I might be wrong ...
> I can see your concerns and as haven't tried it I can't comment.
> However, it is at a block level with only one node able to write to the
> disk so there should be no difference as far as Berkly is concerned.

I've been told that recent DRBD can do active/active, which means to me
that with something like GFS on top of it, you get a filesystem cluster
like having a SAN with a cluster fs.
What also has been discussed on this list several times is that which such
shared filesystem, Cyrus works when using skiplist instead of BDB for the
databases.

Simon

>
> Regards,
>
>  Jack Stone
>
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