From mboxrd@z Thu Jan 1 00:00:00 1970 From: Roy Sigurd Karlsbakk Subject: Re: mdadm vs zfs for home server? Date: Mon, 27 May 2013 21:02:08 +0200 (CEST) Message-ID: <5156525.31.1369681328163.JavaMail.root@zimbra> References: <20130527180912.GA6068@septictank.raw-sewage.fake> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <20130527180912.GA6068@septictank.raw-sewage.fake> Sender: linux-raid-owner@vger.kernel.org To: Matt Garman Cc: linux-raid List-Id: linux-raid.ids Short answer: ZFS will guarantee the data is free of errors, but MD wil= l give you the flexibility of moving between RAID levels and adding dri= ves 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 bec= ause 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. Tha= t will required block pointer rewrite, something that's been talked abo= ut 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? >=20 > 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. >=20 > 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). >=20 > 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. >=20 > 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? >=20 > 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. >=20 > 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"? >=20 > 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. >=20 > Thanks, > Matt >=20 > -- > To unsubscribe from this list: send the line "unsubscribe linux-raid" > in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html --=20 Vennlige hilsener / Best regards roy -- Roy Sigurd Karlsbakk (+47) 98013356 roy@karlsbakk.net 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 element=C3=A6rt imperativ for alle pedagoger =C3=A5 unng=C3=A5= eksessiv anvendelse av idiomer med xenotyp etymologi. I de fleste tilf= eller eksisterer adekvate og relevante synonymer p=C3=A5 norsk. -- To unsubscribe from this list: send the line "unsubscribe linux-raid" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html