Re: [MooseFS-Users] Real experiences from real users

[Marin B. <li...@ol...>]

> > We have experienced all sorts of disasters, crashes, bad drives,
> > etc and
> > were always able to recover using a metalogger or other backups
> > with no
> > data loss (expect on the fly data).
> 
> I'm really interested in this.
> How MFS react to disk failures (or disk still working but with some
> URE) ?
> Is it safe to use MFS without any RAID, as suggested in the official
> site ?

Disks with I/O errors are automatically marked as damaged. You may
configure the threshold in mfschunkserver.cfg. It is perfectly safe
(and recommended) to use MFS on JBOD.

A chunkserver will *never* send bad data, because it always checks the
checksum of a chunk before returning it. Bad chunks would simply be
dropped.

> > Note: The imap email storage is a funny use case. It works really
> > well,
> > but it really balloons storage space because of the small files.
> > Plan
> > for as much a 5x-7x needed capacity.
> 
> Why? 64MB chunks should be useless in email hosting.
> If a file is smaller than 64MB, chunk will get the real file size.
> Why we should plan for 5x-75x needed capacity ?
> 

Yes, but the minimal sector size in MooseFS is 64k, and a chunk cannot
be smaller than that.