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Thread: Understanding the kernel

  1. #1
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    Hi,

    I'm a new mac user. G4 dual drive 1ghz. I have read that it is good to leave the computer on for several hours so that it can do repairs? If this is so, why does it ned to do repairs? If I need to leave it on, do I put the enrgy saver on certain savings? I do not want to leave it on all night.

    Thanks,
    Laura

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    I would look at the book list for "Mac OS X" or "Mac OS 9" and there is one for each called "Missing Manual" that would really cover the basics. There are some that try to be more aimed at troubleshooting. If you do video or Final Cut Pro, might want to find something to dig into that base.

    Some routines run at night, 3 AM, but that is not necessary. Can't even call it repairs, more like housekeeping. A basic manual would walk through all the features, preferences, and how best to use them. Things like what to do if you use iChat and have a firewall. Adding more drives, cables, fan noise, SCSI vs. IDE vs. FireWire.

    Of course before anything, a backup, additional RAM (new to 10.2.3 is that the system is using much more RAM on bootup, the system itself needs 256MB before you do anything, so anyone with 512MB will even feel a pinch), extra backup drive, come first. Basic maintenance. And you can run those housekeeping jobs manually. there's daily, weekly, monthly logs that otherwise get too large and need to be pruned and rotated.

    Ask and you'll get a boatload of ideas that'll talk your ears off :-)

  3. #3
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    I have never heard of leaving any computer on for several hours to do repairs. Can some wise guru educate me otherwise? If you start a specific task or program which takes hours, then obviously you leave it on; but what is the purpose otherwise?

    Laura, where did you read this? I have been using my good old G3 for five years, and now the new G4 at home, and I have never left them on for the sake of repairs. I would love to hear what lengthy repairs the computer does by itself -- i. e. not assigned by me.

    Energy saver settings is at owner's pleasure. On mine I never let the computer fall asleep by itself; display sleep is set separately. When I plan to be away for several hours, I put it to sleep manually. And when I go to sleep, my computers are off -- not merely sleeping, but shut off.

    marrand


    [This message has been edited by marrand (edited 29 December 2002).]

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    Both my 7500 G3 400, and my QS 733 run an "indexing" at 12 midnight. Usually things are shutdown at that time. I manually do it once a week or when I think of it. I can not think of any real "repairs" that happen.

    Follow Gregory's advice... A backup hard drive, basic maintenance and you can run those housekeeping jobs manually at your connivence. Get "OS X The Missing Manual" it can be had for under 20 bucks at amazon.com

    You'll be fine.

    Randy

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    Hi all yerselves,

    ?Just to throw in a 1/2 worth I never shut my computer down. Well, almost. If I leave town for a couple of days I will but other than that-24/7. I don't even sleep the thing now that we have a Unix kernel. I hate sleeping drives, especially on any kind of short timer, I believe that drives last longer kept at speed and temperature than those allowed to spin up/down and heat up/cool down on a regular basis.

    ?I have never been a sys admin type but those who are tell me that Unix systems benefit from a 'longer they are up and running, the more stable they are' policy. I can see where the background housekeeping, that Gregory mentions, being kept to a rigorous schedule might make for a better and more reliable system. My knowledge of this is mostly second hand and I would certainly be open for insights into this. I have had little difficulty for literally YEARS keeping my systems up and running all the time, even before OSX. And before I got a computer with factory installed IBM Deskstar hard drives I had never lost a drive. (I lost two of the Deathstars in a year)

    ?I have run auto synchronization programs that in the night will backup my hard drive to another computer. I did that in OS9 and though I have trouble with the programs I still do it now in OSX after I go to bed. That makes it hard to do shutdowns.

    ?I don't know of anyone that says "You must sleep/shutdown/leave running". I have never ever heard of any kind of consensus as to the best way. So I guess you'll have to invent your own reasons and do what suits your habits.

    Rick
    lost in the possibilities
    My favorite: quis custodiet ipsos custodes

  6. #6
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    Thanks for all the information. Boy, I really have alot to learn. I didn't know I was supposed to do maintenance, nor that the computer does its own.

    Two questions: what would a back up drive be?

    I have the "missing Manual" for Jaguar, but no mention of maintenance, housekeeping, etc. in the index. I guess I check in the individual chapters?

    Laura

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    Backup use to be done to tape cartridges, and well, still is in some environments. but most users use...

    CD/DVD for burning their backup. Small, slow, reliable, easy to move to another computer or off-site for emergency backup (fire, tornado, etc).

    FireWire drive - buy a case and add your own choice of drive (best probably), or buy one with both, pay extra. You don't know what you get, and putting a drive in case is... well, a 'snap.' very easy.

    Another internal IDE drive.

    External SCSI if you want speed, probably have SCSI already, more reliable than FireWire as well.

    With 120GB IDE drives $120-150; and FW case kit $60-150, might be $200-300.
    SCSI means controller ($349), plus $200-400 for 36GB, cable & terminator $175-225, drive case $110.

    With SCSI you can have very fast RAID for scratch, another for backup, but you can spend $2500 (shees! don't tell anyone until they're hooked on SCSI and speed).

    Dantz Retrospect, FWB Backup Toolkit, Carbon Copy Cloner, Synchronize! Pro 2.0, there are a number of backup software packages to help with your backups.

    Daily backup of the day's changes and projects; weekly backup of downloads etc. and even monthly backup of system. rotate two backup sets in case something goes wrong during a backup or failure (or lightning) you've got another.

    Backup your OS X system volume before updates or installing something. Say you want to backout installing OS X 10.2.5, or Office.X update, or, horrors, you installed Norton and now can't uninstall... you have OS X on another volume, you burned a copy to DVD or CD (CDs are small but popular for backups too). Even a ".dmg" (Disk Copy mountable image file) can be a "backup."

    The Gurus had a web page on weekly routine of running Disk Warrior, Disk First Aid, and today, you'd need to add "running Repair Permissions: DAILY" to the 'housekeeping' to keep the byte bugs and dust bunnies in check.

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    Windows XP does some maintenance while idle to 'defrag' the system startup cache by moving it into a hidden set of blocks, sort of like a disk volume, so it is at the front and fastest part of the drive, and also, not scattered across the disk volume.

    I put a large 4GB "holder" file (Disk Copy DVD image), then, after installing the system and all the rest, delete the file and now, all new files are at the front, especially useful for an OS X system only volume. And insures that you'll have enough free space (OS X on less than 8GB is probably too small unless you have an older Mac and must).

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    Hi all -

    Can't tell you exactly what the maintenance that occurs if your Mac is left on (OS X only), but here is some info that points to when it happens. The following is from Versiotracker, the app is called MacJanitor:

    MacJanitor - 1.2

    Runs the system's 3 maintenance scripts

    What's new in this version:

    * Mac OS X Keychain integration
    * 'Run All' function to run all 3 maintenance scripts
    * Ability to cancel operation in progress
    * 'Path bug' fixed.


    Product Description:
    Freeware utility to run the system's daily, weekly, and monthly maintenance scripts (located at /etc/daily, /etc/weekly, and /etc/monthly).

    These scripts are normally run between 3am and 5am, and will not be run if you shut off your Mac at night. This will allow log files to grow very large, and prevent system databases from getting backed up.

    With MacJanitor, you can run these scripts 'by hand' periodically without having to use the Terminal to keep your Mac OS X machine in top racing form.

    Excellent for laptop users and others who shut off or put their Macs to sleep at night.





    Here is the link if you want to read more (or try it):
    http://versiontracker.com/moreinfo.fcgi?id=10491&db=mac

    Read the user reviews (with much salt) for more insight on what OS X does if you leave it on continuously.

    I don't use MacJanitor (and there are other apps that claim the same), just pointing out that on a Unix box (OS X), there ARE daily/weekly/mothly maintenance routines.

    FWIW, don't forget that some of the most reliable boxes (all OSs) in world run 24/7. I agree with Ricks; as with most mechanical things, constant speed causes less wear than repeated starting/stopping. Don't be afraid to leave a machine on for a week at a time, and just have the monitor sleep. My understanding is that without a monitor, an idle system draws only a tiny amount of electricty.

    [This message has been edited by newbie (edited 30 December 2002).]

  10. #10
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    Laura,

    ?I back up everything. Well, almost, Now Gregory, he backs up EVERYTHING. I just back up my Users Directory and Applications.

    ?In OSX backups are interesting to accomplish, there are many issues such as permissions and hidden files that get in the way of a simple command to "check the contents from drive A, compare to drive B and copy the differences.

    ?You can use a program to do that, and on a regular schedule. There are also programs that do regular snapshots of your data and store those in archives in case the worst happen.

    ?For me a daily copy of my data to another drive and a nightly copy of my data to another computer suffices. Use a program like Carbon Copy Cloner, a shareware utility, or SynchronizeProX, a commercial product to do this. This leaves me with a clone of my hard drive on another drive or another computer, protection through redundancy.

    ?The program Retrospect is an archival system where regular (weekly or less often) full volume backups are stored and then snapshots are taken of volume differences in a daily/hourly or whatever schedule. This system traditionally uses removable media storage for archival. Something like tape drives or in smaller setups CDs.

    ?Backups are essential. There are two types of computer users: Those that have had a data loss and those that will. And the second group contains everyone in the first group. There is only one irreplaceable part of your computer, your data. Protect it. I don't care if it is in a PC, a Mac or a Network File Server, it needs a method where you have regular backups.

    ?Drives can fail, viruses can eat data or ruin the file system, users can erase or corrupt data stores(the most common data loss cause) or even worse, you can have a fire or other major calamity. Think of the hours of work you'll have in your website when it is near completion and realize that if it is stored in one place that if something happens to it it is gone.

    ?I would guess that less than 1 percent of PC users have any backup plan at all. And you would not believe the sob stories about emails and pictures of the grandkids lost that flood the help forums. Backup plans will reduce that to a trickle.

    ?Something else for you to read up on.

    Rick
    ?

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    Laura,
    Are you as confused as I by all this marvelous advice?
    I stick to simple basics.
    1. Computer repairing itself? I pay no attention to this. Perhaps unix and windows XP were designed to "repair themselves", but I feel certain that these repairs are effected during normal operation (when the user sits and thinks or goes out for coffee), and one does not need to keep the machine running extra hours. If there were such a need, then it would be spelled out in manuals.
    2. On/off vs. running all the time. I have not seen any hard evidence or proof that one way or the other is better. The simple fact is that all drives will wear out eventually. How fast? That will depend not only duty cycle (on/off vs. on all the time) but also on how well the particular drive was built. There are great drives, there are lemons, and there are many inbetween. Quality control and mechanical complexity probably have greater influence on life span than on/off vs. on. If you sleep better knowing that your mac is shut off, then by all means -- shut it off.
    3. Backups. There is no compromise here -- thou shalt back up or else be punished severly in hell. Period. No ifs, ands or buts about it. What media to use? What software to use? What regimen to use? Well, there are many ways of getting there, and the gurus will give many great options -- simply choose the one you feel most comfortable with and start backing up.
    4. Maintenance. Yes, maintenance is required, even for Windows systems. An obvious one is defragging; another is clean up of temporary internet files. Whatever you can't get from manuals is or will be in these forums.

    marrand

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    Starting up a computer puts the most stress on all the components. Change in temperature, voltage, etc. In the old days on mainframes, it took a lot of juice to power up 10lb disk drives that fit in "pizza oven" drive cases, and you'd have 6, 12, or more disk drives and a very loud noisy room, and it would take 20 minutes or more to bootup a system. If you have any scsi disk drives, they like to have warm up period - like a runner stretching before a workout, to get the temperature up to normal. How hard is it? depends. Does it wear it down? yes. There are xxx start/stop cycles in a drive's lifetime.

    Olde rull of thumb was, if you plan to use it in the next 8 hrs, leave it on. It costs more to turn on/off/on than leave it on. TV sets are on "standby" so that they don't take forever to 'warm up' cause people didn't like having to wait an extra 2-3 minutes. Computers with 'deep sleep' can use left than older Macs that were off but had no deep sleep.

    Unfortunately, the only "manuals" nowadays are things like "Mac OS X: Missing Manaul" or "Disaster Relief" or "OS X Unleashed." And Apple's Knowledge Base which is easy to search, constantly updated, and uses "google" so you know it works with even a simple phrase.

    I know folks who have never heard of a modem surge protector, but fry their modem with all the storms we get and don't realize it isn't necessary. Anything on 24/7 probably should have a UPS (uninterruptable power supply) for safety.

    I've been scared to let my system sleep overnight because two PCI cards didn't yet have firmware support for "advanced power management" (deep sleep) and my Blue & White G3 doesn't support deep sleep but either the OS or a card would try to, and I'd have a kernel panic, a damaged disk drive directory, or worse. It's getting better, just last week ACard (and therefore SIIG) had a firmware update posted to deal with deep sleep for their PCI IDE cards.

    I encourage people to look up the reviews and reliability of various drives in the databases over on www.storagereview.com - and add your own - so that there is a clear pattern if there are defective models. There was/is issues with Maxtor, with the 75GXP IBMs (made in Eastern Europe and lacking the Lucent DSP control chip) that have high failures. IDE/ATA drives now have very short one year warranty (IBM has 3 yr but is cuttiing to 1 yr in another month or so. Whenever I"ve had a drive fail, IBM has had a replacement in my hands within a week, everyone else has taken 3-6 weeks). One year is not a long time. SCSI drives still are made to last (5 yrs) if used properly, and will run for 5 yrs if left on! Turning those puppies on/off, well, you can hear them when they startup, and even shutting down OS X takes much longer when there are SCSI drives attached... not sure why.

    Disk drives today spin at 5400, 7200, 10K, and 15K. There was a time when 3600 rpms seemed fast. Keeping it spinning is one thing, bringing it up to those speeds is where the stress is, along with factors like temperature, humidity. Hot/cold, expansion and contraction, are what cause errors and "bad blocks" and just wear and tear. That's part of why disk drive platters have moved to glass. Metals do show wear and 'fatigue.' You may have a bimetal thermostat. You do not want your disk drive to be a metal. YOu want metal casing to disipitate heat though.

    A little tiny read/write head, a couple molecules above a platter, spinning @ 10,000 rpm, well, it makes my head spin just thinking!

    [This message has been edited by Gregory (edited 30 December 2002).]

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    Gregory...your diligence....steady,earnest,energetic.....in replys to all and every are to be applauded... (pretty obvious he never shuts down!) thanks!

    [This message has been edited by babbkutz (edited 30 December 2002).]

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    Hi everyone,

    Well, I've sat and read the posts and want to thank everyone for their input.

    I can see I've been one of the 99% of the population that Rick talked about who have done nothing to back up/maintain/repair. I've been using a computer for just 3 years now. After getting an awful virus, duh...I started using an anti-virus, etc. That's about the extent of things until now.

    I haven't ever done even the general maintenance things like defragging, etc. Nor have I even back up my files on amything, until I finally got some cd's a couple days ago and actually copied my project files onto them.

    So, I'm starting slow and working my way up. I'll keep on copying files to cd's, explore other ways of backing up files and get instructions about defragging, etc. my laptop and desktop. After attempting that, I'll move on to the more complex things. Also, I see that I can leave my computer on for a couple hours and it will be fine.

    Laura

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    I'll leave the specfics of defragging for Rick and Gregory to answer... but I believe they will tell you not to, as general maintenance. And rather have you backup and initilize/erase instead.

    1.3 more cents
    Randy

  16. #16
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    Hello, all!

    I'm one of those who *never* shuts down a computer unless I have to. I first learned of this back in my mainframe days, and we'd have machines running nonstop for months, take 'em down for maintenance (clean air filters, stuff like that) and...on bringing them back up, *that's* when the machine would have problems.

    Electronic gear, modern motors, all do best left running. The only on-going wear is in bearings and brushes (in hard drives!), but they've gotten so good that 5 years may be the spec, but far longer is normal -- if they're not power-cycled too often. I believe Gregory's spot on about each electromechanical device having a power-cycle life.

    The maintenance that's done over night on Unix machines is run out of a facility called "cron", a table-driven daemon (unattended service program) that runs commands in the background on behalf of users, including the root user. newbie's called it right via the MacJanitor reference: the daily, weekly, monthly "scripts" (interpreted programs) run on OSX at 3:15, 4:30, and 5:30 in the morning, every day, every Saturday, the first of each month repectively.

    Wanna see? Launch Terminal and enter cat /etc/crontab to see the schedule data(*). The scripts were renamed in Jaguar, and now are files stored in subdirectories the /etc/periodic directory ("folder") named, to be obvious, 'daily', 'weekly', and 'monthly'. The individual scripts will be run in alpha-numeric order.

    (*) Note: the 'cat' command is used to concatenate files. Give it a single filename and it prints its contents out, by default to your terminal window. This is really safe to do! Especially with human-readable files like the crontab file.

    These scripts really *are* housekeeping in nature: recycle logfiles, manage junk files (which and why they exist is another subject), do security checks.

    If you like shutting down or sleeping your machine, you really have three choices:

    1. Ignore the housekeeping programs. Your logfiles will get very large.

    2. Run them manually (cf. MacJanitor). What a hassle! That's why cron was invented in the first place.

    3. Change the schedule. (Let me know if you want to and I'll show you how.)

    With either 2 or 3, you're accepting the hit of these sometimes *very* busy programs running during times when you're likely to be using the machine for other purposes, which is why the default schedule in in the wee hours.

    Again: I leave my machines on all the time and let cron do housekeeping when it's unlikely I'm trying to do something else on the machine (between 3:00am and 6:00am).

    Jazzbo

  17. #17
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    Mantra: don't defrag (hummm) don't defrag (hummm) ... repeat until you feel a greater calm come over you.

    Defragging is too risky for its minimal gains unless the filesystem you're running it against is causing performance problems and you believe fragmentation is the cause. In that case, use Gregory's trick of copying all the files (CCC or ditto -rsrcFork) to another volume, erase the contents of the volume in question, and copy back.

    Do *not* consider fragmented directories to be a problem! I can think of no safe way to defrag directories (at least per *my* definition of safe).

    Jazzbo

  18. #18
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    Our Father, Who art IBM,
    Holerith be Thy name.
    Thy paging drum,
    Thy disks be run,
    At 3600 RPM.

    (Heh-heh: 1970s!)

  19. #19
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    hehehehe....you folks are amazing.

    I think I'm afraid to leave the computer on all night because it might blow up. Yes, in my mind I'm still in the typewriter age. I'm hand writing my books. Both my brothers are computer programmers and practically had heart attacks when I bought my first computer a couple years ago.

    Anyway, in terms of housekeeping....since I don't want to manually do all that stuff, what if I start by leaving it on overnight once or twice a week? Would that do any good?

    As far as all the back up processes besides cd back up of files, etc., I need to sit and read through all the info. If there are websites, etc. on backing up, etc. that would be be educational for me, please let me know. I see I missed taking care of computers 101.

    Laura

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    Without doubt Jazzbo, Ricks and Gregory among other members are amazing. I have learned more in 2 years reading here at the Guru's than the previous 15 years of working with Macs.

    This site and people on it really do

    Randy

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