From mboxrd@z Thu Jan 1 00:00:00 1970 From: Duncan <1i5t5.duncan@cox.net> Subject: Re: Balance RAID10 with odd device count Date: Wed, 22 Feb 2012 11:48:20 +0000 (UTC) Message-ID: References: <20120221010724.GB5350@carfax.org.uk> <20120221012148.GD5350@carfax.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 To: linux-btrfs@vger.kernel.org Return-path: List-ID: Hugo Mills posted on Tue, 21 Feb 2012 01:21:48 +0000 as excerpted: > On Mon, Feb 20, 2012 at 08:13:43PM -0500, Tom Cameron wrote: >> On Mon, Feb 20, 2012 at 8:07 PM, Hugo Mills wro= te: >> > >> > =C2=A0 However, you can remove any one drive, and your data is fin= e, >> > =C2=A0 which >> > is what btrfs's RAID-1 guarantee is. I understand that there will = be >> > additional features coming along Real Soon Now (possibly at the sa= me >> > time that RAID-5 and -6 are integrated) which will allow the >> > selection of larger numbers of copies. >> > >> > >> Is there a projected timeframe for RAID5/6? I understand it's curren= tly >> not the development focus of the BTRFS team, and most organizations >> want performance over capacity making RAID10 the clear choice. But, >> there are still some situations where RAID6 is better suited (large >> pools of archive storage). >=20 > Rumour has it that it's the next major thing after btrfsck is out > of the door. I don't know how accurate that is. I'm just some bloke o= n > the Internet. :) The report I read (on phoronix, ymmv but it was supposed to be from a=20 talk at scalex, iirc) said raid-5/6 was planned for kernel 3.4 or 3.5,=20 with triple-copy-mirroring said to piggyback on some of that code, so=20 presumably 3.5 or 3.6. Triple-copy-mirroring as a special case doesn't really make sense to me= ,=20 tho. The first implementation as two-copy (dup) only makes sense, but = in=20 generalizing that to allow triple copy, I'd think/hope they'd generaliz= e=20 it to N-copy, IOW, traditional raid-1 style, instead. I guess we'll see. =46WIW, I'm running on an older 4-spindle md-raid1 setup now, and I had= =20 /hoped/ to convert that to 4-copy btrfs-raid1, but that's simply not=20 possible ATM tho a hybrid 2-copy btrfs on dual dual-spindle md/raid1s i= s=20 possible, if a bit complex. Given that the disks are older, 300 gig sata seagates nearing half thei= r=20 rated run-hours according to smart (great on power and spinup cycles=20 tho), now's not the time to switch them to dual-copy-only! I'd think=20 about triple-copy, but no less! Thus, I'm eagerly awaiting the=20 introduction of tri- or preferably N-copy raid1 mode, in 3.5-ish. But=20 the various articles had lead me to believe that btrfs was almost ready= =20 to have the experimental label removed, and it turns out not to be quit= e=20 that far along, maybe end-of-year if things go well, so letting btrfs=20 continue to stabilize in general while I wait, certainly won't hurt. =3D= :^) Meanwhile, I'm staying on-list so as to keep informed of what else is=20 going on, btrfs-wise, while I wait for triple-copy-mode, minimum. --=20 Duncan - List replies preferred. No HTML msgs. "Every nonfree program has a lord, a master -- and if you use the program, he is your master." Richard Stallman -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" = in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html