Wandering Thoughts archives


Using fully mirrored system disks on Linux

I'm on record as building systems that use mirrored system disks with plain /boot and swap partitions (that is, non mirrored, just duplicated), mostly through ancient caution.

You know what? I was wrong. Totally wrong. I've now built a system with a fully mirrored system disk and not only does it work, it works better than my old way. I will henceforth now mirror /boot and swap, in addition to all of the regular filesystems, on all future systems that I build with mirrored system disks.

With /boot, mirroring keeps things in sync automatically, and it means that the system will come up without manual intervention when there's only one disk. With a /boot and a /boot2, not only do you have to keep them in sync by hand (in practice we don't), but if a disk fails the system will pause in boot because one of your filesystems isn't there and you have to fix it by hand.

With swap, you probably don't need that much swap, it works, and while init scripts seem to be much more tolerant of missing swap areas than missing filesystems I don't see any reason to take chances if I don't have to. And 'mirror everything' is a very simple rule to keep straight.

(I don't have any idea of the performance tradeoffs of mirrored swap versus non-mirrored swap, but my view these days is that if you are worried about the performance characteristics of your swap space, something horrible has gone wrong to start with.)

linux/GoingFullyMirrored written at 23:48:40; Add Comment

How not to improve your CD player application

This is one of the rare entries that I have to present in pictorial form.

Here is a 65% size view of what kscd, the KDE CD playing program, looks like in Fedora 8 (where it is version 1.6, from KDE 3.5.10):

Fedora 8 KsCD

Here is what it looks like in Fedora 10, again 65% size:

Fedora 10 KsCD

(Links to full sized versions are here and here. Note that the Fedora 10 version is a shaped window; the black areas are normally transparent.)

One of these two applications is useful. The other one has been 'improved', presumably because people thought that the first one looked kind of boring (also, apparently, people wanted to be able to give the CD player 'skins'; there are several supplied with Fedora 10's kscd, all of them equally bad). In the process it has been made less useful and even less functional (they are playing the same CD, but only the older one displays the artist correctly).

Apparently I now need a new CD player program, just like last time. Which is a real shame, because kscd was a nice CD player once it started working reliably in Fedora 8.

(Alternately I need to figure out how to build the Fedora 8 version of kscd on Fedora 10. Hopefully the KDE libraries are compatible enough.)

linux/NewCDPlayerNeeded written at 21:31:40; Add Comment

Frustration for a sysadmin (well, for me)

To amplify on a previous entry, I've found that the biggest thing that gets under my skin as a sysadmin, that really leaves me frustrated and short-tempered, is being helpless. Well, not exactly helpless in general; what I mean is being faced with a situation where there's a technical problem (something within my sphere) but there is nothing that I can do, or nothing useful (where I know I am just flailing around, taking random stabs completely in the dark).

This might seem counterintuitive to outsiders, because sysadmins spend a lot of time troubleshooting problems; if doing this frustrated me that much, you'd think that I'd have gotten into a less annoying field by now. But even with apparently mysterious system problems there are usually a lot of things that we can do to diagnose things and to move forward, to at least get closer to a solution; we have piles of tools and techniques and so on. Even if we're not solving the problem right now, we're productively working on it.

(Well, in theory. In practice it can be both tedious and mysterious to try to run down a problem as you diagnose just what's going on; I have spent more than enough time waiting for test runs to finish and the like.)

However, every so often these tools and techniques run out, or I'm stuck in a situation where they're not available; then there's no feeling of productive work, no forward motion on the problem, no nothing, and I am sitting there helpless and powerless. That's when it all gets to me, sometimes badly.

(My classic weak spot is trying to make various sorts of serial connections work; there are so many different things to go wrong, and basically no troubleshooting tools.)

sysadmin/WhatFrustratesMe written at 01:10:42; Add Comment

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