Short answer: ZFS will guarantee the data is free of errors, but MD will give you the flexibility of moving between RAID levels and adding drives to existing RAIDs. I have been working with ZFS with some 400TB of storage, and I considered using it for my home server, but chose MD because of the flexibility in there. ZFS requires you to plan your setup. It allows you to add VDEVs, but data isn't balanced over the VDEVs. That will required block pointer rewrite, something that's been talked about for at least four years, but yet hasn't surfaced.
just my 2c
roy
----- Opprinnelig melding -----
> Anyone out there have a home (or maybe small office) file server
> that where they thought about native Linux software RAID (mdadm)
> versus ZFS on Linux?
>
> I currently have a raid6 array built from five low power (5400 rpm)
> 3TB drives. I put an ext4 filesystem right on top of the md device
> (no lvm). This array used to be comprised of 2TB drives; I've been
> slowly replacing drives with 3TB versions as they went on sale.
>
> I run a weekly check on the array ("raid-check" script on CentOS,
> which is basically a fancy wrapper for "echo check >>
> /sys/block/mdX/md/sync_action"). I shouldn't be surprised, but I've
> noticed that this check now takes substantially longer (than it did
> with the 2TB drives).
>
> I got to thinking about the chances of data loss. First off: I do
> have backups. But I want to take every "reasonable" precaution
> against having to use the backups. Initially I started thinking
> about zfs's raid-z3 (basically, triple-parity raid, the next logical
> step in the raid5, raid6 progression). But then I decided that,
> based on the check speed of my current raid6, maybe I want to get
> away from parity-based raid all together.
>
> Now I've got another 3TB drive on the way (rounding out the total to
> six) and am leaning towards RAID-10. I don't need the performance,
> but it should be more performant than raid6. And I assume (though I
> could be very wrong) that the weekly "check" action ought to be much
> faster than it is with raid6. Is this correct?
>
> But after all that zfs reading, I'm wondering if that might not be
> the way to go. I don't know how necessary it is, but I like the
> idea of having the in-filesystem checksums to prevent "silent" data
> corruption.
>
> I went through a zfs tutorial, building a little raid10 pool out of
> files (just to play with). Seems pretty straightforward. But I'm
> still much more familiar with mdadm (not an expert by any means, but
> quite comfortable with typical uses). So, does my lack of
> experience with zfs offset it's data integrity checks? And
> furthermore, zfs on linux has only recently been marked stable.
> Although there is plenty of anecdotal comments that it's been stable
> much longer (the zfs on linux guys are just ultra-conservative).
> Still, doesn't mdadm have the considerable edge in terms of
> "longtime stability"?
>
> As I said initially, I'm in the thinking-it-through stage, just
> looking to maybe get a discussion going as to why I should go one
> way or the other.
>
> Thanks,
> Matt
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-raid"
> in
> the body of a message to majordomo@xxxxxxxxxxxxxxx
> More majordomo info at http://vger.kernel.org/majordomo-info.html
--
Vennlige hilsener / Best regards
roy
--
Roy Sigurd Karlsbakk
(+47) 98013356
roy@xxxxxxxxxxxxx
http://blogg.karlsbakk.net/
GPG Public key: http://karlsbakk.net/roysigurdkarlsbakk.pubkey.txt
--
I all pedagogikk er det essensielt at pensum presenteres intelligibelt. Det er et elementært imperativ for alle pedagoger å unngå eksessiv anvendelse av idiomer med xenotyp etymologi. I de fleste tilfeller eksisterer adekvate og relevante synonymer på norsk.
--
To unsubscribe from this list: send the line "unsubscribe linux-raid" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
