[plug] Filesystems for lots of inodes

[Byron Hammond]

I'm keeping my eye on this thread with great interest.

I'm really curious to see what your findings are and how you got there.

Cheers

from my Tablet

On Tue, 7 Jan. 2020, 8:16 pm Brad Campbell, <brad at fnarfbargle.com> wrote:

> On 4/1/20 12:40 pm, Brad Campbell wrote:
> > G'day All,
> >
> > I have a little backup machine that has a 4TB drive attached.
> >
> > Every night it logs into all my machines and does a rotating hardlink
> > rsync to back them up.
> >
> > Currently there are about 36 directories and each of those has ~105
> > hardlinked backups.
> >
>
> So I thought I was clever in developing a methodlology that would allow
> me to do a few clever tests with new filesystems using existing data.
>
> So, I started with a filesystem on the USB drive and cloned that into a
> (4TB) file for loopback mounting hosted on a quick(ish) RAID-6.
>
> I thought I'd dump/restore that onto a spare partition I keep for
> testing on a scratch RAID-5, but found that dump/restore was good for
> about 2GB/hr in this scenario. So after about 6Gb I killed that.
>
> I thought I could use tar in a pipe to replicate instead, and that
> worked a lot faster (compared to dump/restore anyway). I got ~100G into
> that and had a re-think about making sure I only had to do this once,
> so I used tar piped through pigz and then over the network onto another
> array on a test box.
>
> The theory there was having the whole thing as one big tar.gz meant I
> could untar it rapidly onto different filesystems and test it out.
>
> Nice in theory, but > 48 hours later and it's nearly done. Raw bandwidth
> is fine. When it hits the static backup directory and large files I get
> full network bandwidth (~300MB/s), but it bogs down once it hits the
> rotating hardlinks again.
>
> Interesting, with 800MB/s of disk and 300MB/s of network it's absolutely
> limited by the random IO limitations of the disks. With ~10MB/s of
> actual data the disks are pinned 100% usage with huge latencies just
> dealing with the fragmentation.
>
> So, I *will* test these filesystems, but just getting this thing
> archived in a format where I can replicate it in less than 2 days has
> proven "challenging" so far.
>
>
> --
> An expert is a person who has found out by his own painful
> experience all the mistakes that one can make in a very
> narrow field. - Niels Bohr
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