From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from thunderbird6.fab.redhat.com (vpn-6-21.fab.redhat.com [10.33.6.21]) by ns3.rdu.redhat.com (8.13.8/8.13.8) with ESMTP id n3DCTsqC032024 for ; Mon, 13 Apr 2009 08:29:54 -0400 Message-ID: <49E32F57.8020105@redhat.com> Date: Mon, 13 Apr 2009 13:25:59 +0100 From: "Bryn M. Reeves" MIME-Version: 1.0 Subject: Re: [linux-lvm] Will LVM2 ever be able to do striped mirrors "raid 10"? References: <49DCA275.8070203@Calva.COM> <49DF02A7.50606@Calva.COM> <20090410101959.GA21846@us.ibm.com> <49DF2403.10009@Calva.COM> In-Reply-To: <49DF2403.10009@Calva.COM> Content-Transfer-Encoding: 7bit Reply-To: LVM general discussion and development List-Id: LVM general discussion and development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , List-Id: Content-Type: text/plain; charset="us-ascii" To: LVM general discussion and development -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 John Hughes wrote: > malahal@us.ibm.com wrote: >> John Hughes [john@Calva.COM] wrote: >> >>> John Hughes wrote: >>> >>>> if (lp->stripes > 1) { >>>> log_error("mirrors and stripes are currently " >>>> "incompatible"); >>>> return 0; >>>> } >>>> >>>> Should I just stick with mdadm for my mirroring and striping needs? >>>> >> >> You can do it today with some hassle or wait until someone implements a >> feature called 'generic layering'. The feature really means, treat some >> LVs as PVs! >> >> How can you do raid10 today? Create two raid0 LVs. Lets us call these >> lvgroup0/lv0 and lvgroup0/lv1. Now create raid1 lv in lvgroup1 where >> lvgroup1's PVs are lvgroup0/lv0 and lvgroup0/lv1. >> >> Isn't that a rai10 volume? No, it's a RAID 0+1 (RAID01/mirror of stripes). > To increase the chances of surviving a double-disk failure it would be > better to raid-0 a bunch of raid-1's. This is RAID1+0 (RAID10/stripe of mirrors) - it's usually preferable to 0+1 not only because of the improved redundancy but also the individual mirror sets can have failures and recover independently. When a strip set in a RAID0+1 fails the entire mirror must be re-synchronised giving longer recovery times and more performance degradation during the rebuild. > Are we sure there are no deadlock problems with LVM2 layered on top of > LVM2? Stacked volumes work fine, there's just limited support in the tools for creating them without going to a lot of manual effort at the moment. Regards, Bryn. -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.9 (GNU/Linux) Comment: Using GnuPG with Fedora - http://enigmail.mozdev.org iEYEARECAAYFAknjL1cACgkQ6YSQoMYUY96uPACeNwylwf1aeZuAzYxHWGJhH7Je LHMAnjLy4NB77gUiABVUkiKeCAMpbGU4 =lv0v -----END PGP SIGNATURE-----