From owner-freebsd-hackers Mon Sep 30 17:57:19 1996 Return-Path: owner-hackers Received: (from root@localhost) by freefall.freebsd.org (8.7.5/8.7.3) id RAA11650 for hackers-outgoing; Mon, 30 Sep 1996 17:34:47 -0700 (PDT) Received: from who.cdrom.com (who.cdrom.com [204.216.27.3]) by freefall.freebsd.org (8.7.5/8.7.3) with ESMTP id RAA11530 for ; Mon, 30 Sep 1996 17:34:34 -0700 (PDT) Received: from answerman.mindspring.com (answerman.mindspring.com [204.180.128.8]) by who.cdrom.com (8.7.5/8.6.11) with ESMTP id PAA22125 for ; Mon, 30 Sep 1996 15:46:34 -0700 (PDT) Received: from borg.mindspring.com (borg.mindspring.com [204.180.128.14]) by answerman.mindspring.com (8.7.5/8.7.3) with ESMTP id SAA16648; Mon, 30 Sep 1996 18:46:12 -0400 (EDT) Received: from bogus.mindspring.com (user-168-121-39-4.dialup.mindspring.com [168.121.39.4]) by borg.mindspring.com (8.6.12/8.6.12) with SMTP id SAA02879; Mon, 30 Sep 1996 18:46:07 -0400 Message-Id: <1.5.4.32.19960930224608.0066dee0@mindspring.com> X-Sender: kpneal@mindspring.com X-Mailer: Windows Eudora Light Version 1.5.4 (32) Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Date: Mon, 30 Sep 1996 18:46:08 -0400 To: James Graham From: "Kevin P. Neal" Subject: Re: VPS mailing list, BSD interest? Cc: hackers@freebsd.org, tech@openbsd.org, current-users@NetBSD.ORG Sender: owner-hackers@freebsd.org X-Loop: FreeBSD.org Precedence: bulk At 12:24 PM 9/30/96 -0700, James Graham wrote: >"Kevin P. Neal" sez: ># >Return-Path: cddukes@unity.ncsu.edu ># >From: cddukes@unity.ncsu.edu ># >Subject: VPS mailing list ># >To: kpneal@pobox.com ># >Date: Sat, 28 Sep 1996 18:43:56 -0400 (EDT) ># > ># >vps-devel@acm.uiuc.edu ># >(And vps-devel-request to manipulate). ># ># Ok, my friend Chris Dukes wants a LVM-like thing for a free Unix. He's workin ># g ># with the Linux guys on creating one fairly similar to the one found on AIX. ># ># The question is, is anybody in the BSD world interested in such a thing? It ># would allow lots of neat things, like extendable partitions. Mirroring ># of logical partitions, etc. > >What, aside from extendable partitions, would LVM give us over CCD? > > --*greywolf; >From an overview of the AIX system that Dukes has lying around in his directory at NCSU: >Logical Volume Storage Overview >A hierarchy of structures is used to manage fixed-disk storage. Each individual >fixed-disk drive, called a physical volume (PV) has a name, such as >/dev/hdisk0. Every physical volume in use belongs to a volume group (VG). >All of the physical volumes in a volume group are divided into physical >partitions (PPs) of the same size (by default 2MB in volume groups that include >physical volumes smaller than 300MB, 4MB otherwise). >Within each volume group, one or more logical volumes (LVs) are defined. >Logical volumes are groups of information located on physical volumes. Data on >logical volumes appears to be contiguous to the user but can be discontiguous >on the physical volume. This allows file systems, paging space, and other >logical volumes to be resized or relocated, span multiple physical volumes, and >have their contents replicated for greater flexibility and availability in the >Each logical volume consists of one or more logical partitions (LPs). Each >logical partition corresponds to at least one physical partition. If mirroring >is specified for the logical volume, additional physical partitions are >allocated to store the additional copies of each logical partition. Although >the logical partitions are numbered consecutively, the underlying physical >partitions are not necessarily consecutive or contiguous. storage of data. >When performing a command or procedure on the rootvg, you need to be familiar >with its unique characteristics. You create a new volume group with the mkvg >command. You add a physical volume to a volume group with the extendvg command >and remove it from a volume group with the reducevg command. Some of the other >commands that you will be using on volume groups include: change (chvg), list >(lsvg), remove (exportvg), install ( importvg), reorganize (reorgvg), >synchronize (syncvg), make available for use ( varyonvg), and make unavailable >for use (varyoffvg). >You may want to create separate volume groups, however, for security reasons, >because each volume group can have its own security permissions. I'm not sure what security permissions are used on volume groups. The document next goes into how you can easily move things around to replace a disk, for example. >A quorum is a vote of the number of Volume Group Descriptor Areas and Volume >Group Status Areas (VGDA/VGSA) that are active. A quorum ensures data integrity >in the event of a disk failure. >When a quorum is lost, the volume group varies itself off so that the disks are >no longer accessible by the Logical Volume Manager (LVM). This prevents further >disk I/O to that volume group so that data is not lost or assumed to be written >when physical problems occur. >There are cases when it is desirable to continue operating the volume group >even though a quorum is lost. >The most common case for a nonquorum volume group is when the logical volumes >have been mirrored. When a disk is lost, the data is not lost if a copy of >the logical volume resides on a disk that is not disabled and can be accessed. >If a disk failure occurs, the volume group remains active as long as there is >one logical volume copy intact on a disk. It's a rather long document, and it gets into much detail in some places. Neat stuff. Resizable partitions, easy mirroring of individual partitions, reorganizing of partitions with ease. Stability in the event of hardware going bad in run time. Imagine taking a system down, hooking up a drive, then booting multi-user mode. In multi-user mode, add partitions and filesystems as you like. Rearrange as you like. Minimized down time. "Help! My home directory partition is full!" "Hold on a sec.....How's that?" "Wow! Thanks!" Sounds like good stuff to me. Much of this is possible to some extent with AFS, but I think it'd be useful at the disk/filesystem level (in there somewhere ;). Note that JFS figures into this somehow, and I'm not very clear on this (Terry?). I don't know how FFS or ext2fs will fit into it, or if they will. LFS? (Terry?). Is Margo Seltzer around? (Would she be able to contribute any ideas?) Her web pages looked cool (I love web pages with white papers online). If anybody thinks this is a good idea, but doesn't have time, at least let me know that somebody else thinks this is neat stuff. -- XCOMM Kevin P. Neal, Sophomore, Comp. Sci. \ kpneal@pobox.com XCOMM "Corrected!" -- Old Amiga tips file \ kpneal@eos.ncsu.edu XCOMM Visit the House of Retrocomputing: / Perm. Email: XCOMM http://www.pobox.com/~kpn/ / kevinneal@bix.com