September 2005 - WLUG - wlug.mailman3.com

Re: [Wlug] Speaking of interesting meetings...

by Bill Smith

Le Wed, 31 Aug 2005 20:56:17 -0400 > This month, I've been debugging USB problems on my server, and I > think I may have made some progress on USB 1.x, but not on USB 2.x. > I'm not sure if this is a meeting topic - howto get stuff to work on > USB and how to debug it if it does not. > > Your thoughts? Does this involve fixing problems with USB devices that have worked with Linux in the past, or it more along the lines of hacking devices that don't have working drivers? -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- William Smith wsmith-at-chezsmith-dot-com Fall River, MA http://www.chezsmith.com The minute you say you can't, you won't... ...and then you fail. * TAG! v3.1a *

Sept. 1, 2005

Re: [Wlug] Re: Wlug Digest, Vol 22, Issue 18

by John Stoffel

Carlton> I've done software RAID (RAID0 and RAID5) for a long time and Carlton> never had to use an initrd image. Just have a 100 MB boot Carlton> partition on one drive, and set root=/dev/md0 in grub. For me, the whole idea of booting of RAID is so that I can lose either disk, and not really notice. Currently, I don't have that. And since my main test system is also my main work system at home, I'm loathe to screw with it much. *grin* Carlton> This is with two 60GB WD HD's and one 80 GB (which has the Carlton> bootable 100 MB partition). If you RAID it all, well, guess Carlton> you need an initrd (please correct me if I'm wrong). As far as I know, yes you do need an initrd (or initramfs now?) to make it work properly. Carlton> As far as RAID1 and RAID5, isn't RAID5 strictly better, if Carlton> you have the HD's? I mean, just lose 1/3 of the storage for Carlton> total mirroring and you have to lose 2 HD's to lose your Carlton> data. Why would someone choose RAID1 over RAID5 (just Carlton> curious)? I did have a RAID5 system set up, but decided to Carlton> change it over to RAID0 and use an external Maxtor drive for Carlton> backup (just simple rsync). RAID0 = stripping RAID1 = mirroring RAID5 = parity RAID5 suffers on write performance when compared to RAID1, since if you write a small chunk of data, RAID5 may have to actually READ/COMPUTE PARITY/WRITE to all the drives. With RAID1, it's a simple parallel write to each drive. No READ overhead. RAID5 can generally just lose 1 disk from the set without losing data. RAID1 can lose 1/2 the mirror without losing data. How you implement your RAID1 setup across more than two disks is an issue. I choose RAID1 over RAID5 because I only had space for two drives, and I only had an HPT302 with dual channels, so I put one disk on each channel for maximum peformance. If I had more money and a 3ware controller, I probably would have gone for RAID5 on my data, since it has a size/cost advantage over RAID1. I would NEVER go for RAID0 for my data, too much potential for data loss. Even with backups. Carlton> Personally, I feel if you compile a couple of kernels it Carlton> really becomes old hat, I mean, once you know how to do it Carlton> it's no big deal. Same with RAID systems. But that would be Carlton> an interesting meeting, nonetheless. Exactly, it would be an interesting meeting to show people how easy it is to implement, and hopefully how robust it is as well, esp if you lose your primary harddisk. Can you boot cleanly from the secondary one? You have updated the MBR on that disk, right? Carlton> I've never had a problem and found I needed initrd to get Carlton> something to work. What are the benefits of using it? >From what I know, the advantage/requirement of using an initrd is that you can boot off of a funky device, since you first boot into a small OS image with all the tools you need to setup and switch to your main filesystems. In my case, I've got a pair of 9gb SCSI disks, and I currently boot off one. My plan has always been to mirror the two disks so that if I lost one, I could still boot. My data is all on a pair of 120gb IDE drives, which are mirrored, and which have saved me from ugly restores, because I noticed that one disk had dropped out and I was able to just re-mirror without any major impact. John

Sept. 1, 2005

Speaking of interesting meetings...

by Andy Stewart

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 ...what do you all propose for a topic for the Sept. 8 meeting? More importantly, does anybody want to do a presentation or lead the discussion? This month, I've been debugging USB problems on my server, and I think I may have made some progress on USB 1.x, but not on USB 2.x. I'm not sure if this is a meeting topic - howto get stuff to work on USB and how to debug it if it does not. Your thoughts? Thanks! Andy - -- Andy Stewart, Founder Worcester Linux Users' Group Worcester, MA, USA http://www.wlug.org -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.5 (GNU/Linux) Comment: Using GnuPG with Thunderbird - http://enigmail.mozdev.org iD8DBQFDFlGxHl0iXDssISsRAneXAJ0Rkqhwc9rkJ60lsWDUKA0UQdNGKQCeKwCG Ed27RqXttkP9STLCkoo2OQ0= =4xsk -----END PGP SIGNATURE-----

Sept. 1, 2005

Re: Wlug Digest, Vol 22, Issue 18

by Carlton C. Stedman II

Re: Bootable RAID system > I keep waffling back and forth between RAID1 (mirroring) and RAID5. > And I keep waffling between booting from RAID or not. Part of the > problem is that to boot off raid, you need to build a intrd image, and > since I do a bunch of kernel compiles and reboots all the time (say > once a week or so...) I've been a bit leary of all that. I've done software RAID (RAID0 and RAID5) for a long time and never had to use an initrd image. Just have a 100 MB boot partition on one drive, and set root=/dev/md0 in grub. This is with two 60GB WD HD's and one 80 GB (which has the bootable 100 MB partition). If you RAID it all, well, guess you need an initrd (please correct me if I'm wrong). As far as RAID1 and RAID5, isn't RAID5 strictly better, if you have the HD's? I mean, just lose 1/3 of the storage for total mirroring and you have to lose 2 HD's to lose your data. Why would someone choose RAID1 over RAID5 (just curious)? I did have a RAID5 system set up, but decided to change it over to RAID0 and use an external Maxtor drive for backup (just simple rsync). > Now that would be a good meeting some evening, talking about and > showing how to setup a bootable RAID system for the OS and how to > upgrade your kernel easily and automatically. Personally, I feel if you compile a couple of kernels it really becomes old hat, I mean, once you know how to do it it's no big deal. Same with RAID systems. But that would be an interesting meeting, nonetheless. > Let me rephrase your reasoning: You don't want to use an initrd because > you aren't familiar with the process. Just because you do a lot of kernel > builds/reboots (and your definition of a lot is my definition of very few, > here), that is no reason not to use an initrd. I've never had a problem and found I needed initrd to get something to work. What are the benefits of using it? - Carlton

Sept. 1, 2005