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

[Gandalf C. <gan...@gm...>]

Il giorno dom 20 mag 2018 alle ore 23:58 WK <wk...@bn...> ha scritto:
> Early on in our MFS history, we *did* have issues with VMs when they
> were under heavy i/o load AND the MFS cluster was busy doing
> rebalancing. They would go read-only and/or lose a chunk, requiring an
> fsck to recover.

Did you have time to figure this out? Why this happened?
It was due to a bug in the older version of MooseFS or something else?

> At the time we stopped using MFS for VM images and purposed MFS solely
> for Email, NAS type File Server loads and Archive backups.

Email will be one of our primary use case.

> Since 3.x we have begun to resume using MFS for "some" VM images with no
> failures, but we are still a little skittish and reserve that for
> 'Cloud-Native' installs where there are other VM copies on other
> hosts/storage, just in case something bad happens.

Why ? Did you have any more issues with 3.x ?

> 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 ?

> a) a Tech brought up a chunkserver with the same IP as another
> chunkserver. Not a good result, as it swiss cheesed the chunkserver data
> on any file that was active during the period.

What happens in this case ? MFS will start to send bad data coming from the
chunkserver with the bad IP ?

> 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 ?

In example, a 2MB file, is saved as 2MB file (plus a little bit overhead
due to the MFS header)