Date: Tue, 1 Oct 1996 09:21:45 -0400 (EDT) From: david_rankin@VNET.IBM.COM To: kpneal@pobox.com (Kevin P. Neal), vps-devel@acm.uiuc.edu Cc: hackers@freebsd.org, tech@openbsd.org, current-users@netbsd.org Subject: Re: VPS mailing list, BSD interest? Message-ID: <9610011321.AA19746@davidr.lexington.ibm.com> In-Reply-To: <1.5.4.32.19960930224608.0066dee0@mindspring.com> from "Kevin P. Neal" at Sep 30, 96 06:46:08 pm
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>Date: Mon, 30 Sep 1996 18:46:08 -0400 >To: James Graham <greywolf@siva.captech.com> >From: "Kevin P. Neal" <kpneal@pobox.com> >Subject: Re: VPS mailing list, BSD interest? >Cc: hackers@freebsd.org, tech@openbsd.org, current-users@netbsd.org Since this message is only marginally useful to the lists its on, and really useful to vps-devel, I'm setting the Reply-To to vps-devel. >At 12:24 PM 9/30/96 -0700, James Graham wrote: .... >Note that JFS figures into this somehow, and I'm not very clear on this >(Terry?). I believe that jfs happens to be AIX's fs of choice, so it's not inherantly necessary to have it too. That said, I would personally prefer to have a journaling file system, one based on a slightly better performer than generic ffs. (I was actually looking at getting the Viva File system going on the Lite-based systems, and then adding journaling and live expansion to it (It's number three on my to-do list). Check out ftp://al.cs.engr.uky.edu/cs/techreports/225-93.ps.Z for info on VIFS.) >I don't know how FFS or ext2fs will fit into it, or if they will. I seem to remember that "der Mouse" had a program to extend ffs level 2 filesystems, although it met with some serious reservations. Perhaps with more work it could be used on non-live filesystems. I don't know how easy it'd be to resize ext2fs. >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 LFS ever gets fixed, this would be a good candidate for extendability, since all LFS is in the end is one large open space. Of course, the devil is in the details. :) >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. I for one am very glad to see this, because it is number two on my to-do list. (Number one is to get enough disk space to do the rest of the list. ;) As soon as my finances allow a NetBSD source tree, I will be happy to throw what personal time I can in on this. Having seen both AIX's and HP-UX's lvm implementations, there's a few implementation ideas I'd like to share: 1> Extendability should be transparent. AIX does this one right IMHO, allowing for live expansion of file systems, HP-UX (at least in 10.01) made you unmount the filesystem. If someone can engineer one of the file systems to live through being shrunk, either on-the-fly or while inactive, even better (but notice I'm not volunteering :). 2> Movable extents. HP-UX LVM (at least) allows one to move all of the extents (*) on one or more physical partitions (no matter how fragmented) onto different partitions while live (leaving the new arrangement physically contiguous). Since this could be real-time work, it'd make moving data between disks even more convenient. 3> Sparse list implementations One flaw I've seen in HP-UX LVM is that the logical extent to physical extent mapping appears to be in array form, which is IMHO too wasteful of kernal memory. Instead, I'd like to see most of the lists in the kernal be sparse. 4> Some RAID functionality I'm very skittish about RAID 5 in software (it's slow enough in hardware), but allowing striping across physical media and/or mirroring across physical media in software is IMHO a Good Idea when used wisely. Certainly a 2 controller machine with disks on each can manage some nice speed increases when the partition is spread across the controlers. David -- David W. Rankin, Jr. External Email: david_rankin@vnet.ibm.com Internal Email: drankin@davidr.lexington.ibm.com or lexgate(drankin) Phone: (IBM Internal) 8-545-1457 (External) 1-606-243-1457 Alpha Pager: 1-606-259-6309
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