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

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

Il giorno mar 22 mag 2018 alle ore 21:00 Marco Milano <mar...@gm...>
ha scritto:
> Assuming that you have minimum of 2 copies in MooseFS, it will read,
detect
> and read from second copy and will heal the first copy.
> So, I don't know what you mean exactly by "does the same" but
> it is not the *same*

You are right, in this case, MooseFS is better because is able to
recontruct the chunk, ZFS don't.

> MooseFS will be *aware* of the corruption during the read and will self
heal
> as I explained above. (Or during the checksum checking (native scrub)
loop,
> whichever comes first.)

Yes, excactly, that's the problem.
Only during a read or a (very, very, very) slow scrub.
ZFS scrub is much faster, but is useless without a RAID.

> You seem to be making these constant claims about "native scrub taking
months",
> but I believe it was explained in earlier emails that this will depend on
your
> hardware configuration. I believe there was another email which basically
said
> this "native scrub speed" was much improved in version 4.
> So I think it is fair to say that you should stop repeating this "native
scrub takes months" claim,
> or if you are not going to stop repeating it, at least put some
qualifiers around it.

Probably is unclear to me how to calculate the chunk loop speed. It's
unclear even with LizardFS (is almost the same).
Let's see:

15.000.000 chunks.

HDD_TEST_FREQ is the frequency for 1 chunk check. Default to 1 seconds.
Lowering it to 1 (will destroy cluster performance, already tried) means 1
full scrub every
15.000.000 seconds.

15.000.000 seconds = 174 days = 6 months.

> Or download v4, and see if the speed improved...

Testing right now....
There is a HDD_TEST_SPEED in MB/s, this could be useful