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Comment Re:BTRFS (Score 1) 191

That sounds better than ZFS. If you actually manage to fill one up 100%, you're (probably) screwed. Due to it's Copy On Write implementation, deleting a file requires free space.
If you have some snapshots, you can drop those to free up some space. If you don't have snapshots to drop, your only option to recover is to enlarge the volume. You can either add another RAID extent (which you can't ever remove), or replace all of the disks with larger disks and expand.

Comment Re:BTRFS (Score 1) 191

Oracle doesn't give away anything they can sell.

ZFS v28 was the last version that was open source, by Sun.
Oracle is still developing newer versions of ZFS, but they are closed source.
I believe ZFS is available in Oracle Linux, but I haven't verified that. I'm not sure how they get around the licensing issues.

Comment Re:For home users, basically meaningless. (Score 1) 191

XFS was designed to be a media filesystem, when SGI wrote it for Irix. It's a good fit.
I plan to use ZFS for my media storage, but there is one important consideration. ZFS does NOT like to be more than 80% full. If you're planning to fill the disks greater than 80%, stick with XFS. I'm not, so I'm going with ZFS. XFS still has issues in this scenario, but it's not as bad as ZFS.

Comment Re:For home users, basically meaningless. (Score 2) 191

It also made just about any computer with less than 8 GB of RAM obsolete.

a) Pick the right tool for the job.
b) ZFS works fine without lots of RAM. Either cap the ARC, or disable it.

I plan to use ZFS for my personal NAS. I'll have 4TiB of storage (spinners) and 2GiB of RAM. It's mostly media storage, so ARC isn't terribly useful. And ZFS will auto-disable the ARC if the machine has less than 4TiB of RAM. Sure, it's not going to set any benchmarks records, but I don't need it to. Streaming media at the home scale isn't taxing for modern PCs.

It's also not very friendly with applications that need large chunks of RAM, like a database or large Java VM application

I love ZFS for my database servers. It plays very well with PostgreSQL, because in PG you can tell it how much RAM to use as a buffer AND estimate how much RAM the OS will use for cache. Just tell PG that the OS will do all the caching, and things are good. ZFS beat the crap out of my HW RAID card in the PG benchmarks, with the same amount of RAM, without adjusting the configs I mentioned.

And lets not forget the other great features it offers:

  • It's beautiful for RAID1. mdadm is weak with partial failures. If a drive has bitrot, mdadm will tell you, but it can't tell you which drive is right. ZFS knows which one is right, and fixes it automatically.
  • Auto expansion is available (disabled by default). I've been upgrading my personal NAS for 15 years, one part at a time. I have expanded the LVM+mdadm ext FS from 100GB -> 250GB -> 500GB -> 2TB. It's easier now that ext3 has online resize, but it's still a lot more work than ZFS.

I do wish ZFS could handle changing the layout on the fly, and shrinking volumes. It's corner case, but it would come in handy in some failure scenarios. Veritas Volume Manager was the only thing I've worked with that did this well, and that was hella expensive. (I consider any software that costs more than the machine that it runs on to be hella expensive.)

Comment Re:CardDav (Score 1) 388

I'm really afraid e-mail is going away though. Most people today would rather message via Facebook and this article goes into how unreliable it is to run your own e-mail server due to Microsoft/Google's over aggressive spam filtering: http://penguindreams.org/blog/...

MS/GOOG didn't start that; SPAM scoring did. I started having delivery problems from my consumer grade connection a decade ago. Now it's virtually impossible to deliver email from an IP address in the dynamic database.

Every ISP I've had runs an SMTP relay (I'm currently on Time Warner). I tell postfix to relay most things through it. I'd prefer not to, but it's going over their wires, so they can already read it if they want to.

[clewis@hacker ~]$ grep 'transport_maps' /etc/postfix/main.cf
transport_maps = hash:/etc/postfix/transport

[clewis@hacker ~]$ tail -4 /etc/postfix/transport
mydomain.com :
.mydomain.com :
myfriend.com :
* smtp:[smtp-server.roadrunner.com]

Whoops. Likes like I should update that config. RoadRunner was bought out years ago. IIRC, I got smtp-server.roadrunner.com from their email client setup instructions.

Comment Re:Diesel electric (Score 1) 230

I could've sworn a local train that navigates a mountain pass had regenerative braking. I appear to be mistaken.

Dynamic Braking (wikipedia link if you prefer) dissipates all of the electricity generated as heat. These trains are clearly referenced as engaging the dynamic braking system during a braking scare in the 90s, and not a regenerative braking system. A 2004 paper obtained dynamic braking data for this train line.

For further evidence, I ran some informal youtube and google searches. There are no videos for "train regenerative braking", but a lot for "train dynamic braking". Google searches only turn up papers for "train regenerative braking", but "train dynamic braking" returns plenty of magazine articles and press releases .

Comment Re:Why? What advantages does this have over ZFS? (Score 1) 132

As a long time ZFS admin, I have a few suggestions.

ZFS snapshots and send are much faster than rsync. Nearly all of them time is spent actually transferring data, and very little is spent enumerating data. One day it dawned on me that I could do hourly, or even 5 minute, snapshot && send on machines that could only handle daily rsyncs on ext4. It still depends on your write bandwidth and overwrite percentage, but it removes number of files from the equation.

Regarding vdev reorganization, it's true, you can't really change vdevs in an existing pool. I got around that by destroying the zpool on the backup server, re-creating it the way I wanted, then zfs sending the FS over again. The actual failover process is part of the manual failover setup anyway, so flipping cost me less than a minute of downtime. Let it burn in for a few days, then rebuild the original server's disks.

One last thing it took me a while to figure out. RAID-Z is faster than RAID10. Even for your IO bound processes, like PostgreSQL or MySQL. I'd done so many benchmarks showing that hardware RAID10 was better than hardware RAID5 for IO load, that I didn't even think about re-testing that conclusion under ZFS. Much later, I noticed that my storage servers (RAIDZ) could handle more IO than my database servers (RAID10). A 4 disk RAIDZ was faster than a 4 disk RAID10, and a 4 disk RAIDZ2 was the same speed. And I had 5 bays for spinners, so I could actually do a 5 disk RAIDZ vs a 4 disk RAID10 (8 bays total, including 3 for mirrored ZIL + L2ARC). As always, your benchmarks will vary. Just don't forget to re-test conventional wisdom.

Comment Re:Net metering is unstustainable (Score 2) 374

The current system lets the home owner use the power grid as a battery, storing excess energy for later use. And this battery is free. But it's not free - someone has to pay for the power lines, meters, and generation or storage capacity that makes it work.

The power grid is only conceptually (and billing wise) treated as a battery. It isn't electrically. The grid doesn't have a set of batteries (and AC-to-DC converters) storing excess solar panel output for later use. Instead, the excess power is consumed by nearby homes that don't have solar panels (the path of least resistance). Billing wise, it is treated as a battery (in a majority of areas), because that makes the billing simple.

I see roof-top solar as a convienence for the generators. It effectively removes load during daylight (ie peak) times, and transfers the load to nighttime (ie, non-peak) times. It smooths out the day/night variances in generation. That only works as long as the roof-top solar production remains smaller than day/night variance, but that's the case we're dealing with now.

Aside from that, I (living in SoCal) do pay a delivery charge on my monthly bill, regardless of my generation or consumption of power. I've no idea how it's computed, and it varies month to month. It doesn't seem to be related to how much I generate or consume in a given month. It's a couple dollars, so I don't really care.

Comment Re:Python for learning? Good choice. (Score 1) 415

I don't do this often, but I do occasionally use indentation that follows the data's logic, not the program's logic.  For example, I've written some XML generation code like:

$xml = new Xml();
$foo = $xml->addChild( 'foo');
  $foo->addAttribute( 'attr', 'bar');
  $foo->addNode( 'foonode', 'foonodevalue');
  $fc1->addChild( 'foochild1');
    $fc1->addNode( 'foochild1node', 'value1');
  $fc2->addChild( 'foochild2');
    $fc2->addAttribute( 'foochild2attr', 'value2');
    $fc2->addNode( 'foochild2node', 'value2');
$xml->addNode( 'xmlnode', 'value3');

Code like this gets large comment blocks above and below stating that I'm using a non-standard indentation, and why.

When I later had to refactor the XML schema, it was incredibly useful to have it indented this way.

It depends on the library and language though.  When I was using nested C structures, or nested object, it wasn't necessary, because the data structure was a lot more visible.  This code is easier to understand using traditional indentation:

$xml = new Xml();
$xml->addChild( 'foo');
$xml->foo->addAttribute( 'attr', 'bar');
$xml->foo->addNode( 'foonode', 'foonodevalue');

$xml->foo->addChild( 'foochild1');
$xml->foo->foochild1->addNode( 'foochild1node', 'value1');

$xml->foo->addChild( 'foochild2');
$xml->foo->foochild2->addAttribute( 'foochild2attr', 'value2');
$xml->foo->foochild2->addNode( 'foochild2node', 'value2');

$xml->addNode( 'xmlnode', 'value3');

Comment Re:Refunds indicate bad tax planning (Score 1) 632

1) Especially right now, that money wouldn't earn much elsewhere

Agreed, I'm not worrying about it, but I will in a couple years.

2) Fewer things to worry about come tax time. There are penalties for under-withholding, at least in some conditions. Overwithholding a little protects you from these.

If you owe more than $1,000, you owe a penalty. Unless you got a refund last year, or you owe less than you did the previous year. The wording is awkward there. Basically the first underpayment is free, and you get a pass while you're trying to fix the problem. I'm pretty sure TurboTax told me this.

3) I am not even sure if it's legal to decrease my withholding, for example.

It is legal, and the IRS has a calculator for you. Intuit has one online somewhere. TurboTax will generate a W4 for you after you do your taxes. However, I hate all of them. They all try to take into account what's been withheld year-to-date, and figure out the magic number to get a $0 refund at the end of the year. And every single one gives me a wildly different number, without showing their work. Which means they're all wrong, and I'll have to try again next year. I finally sat down and figured it out, because fixing it was a couple hundred bucks a paycheck. I hate myself, but I made the largest spreadsheet of my life using the IRS Employer's Withholding publication. I started coding it, but the publication tables mentally mapped better to a spreadsheet. My HR department wasn't willing to help me, and I can't blame them once I finished. Now I just tweak the W4 number up or down by 1, based on if my refund was larger or smaller than last year.

Comment Re:Max RAM? (Score 1) 353

I need to upgrade the shared family desktop from 10GB to 16GB. Every user logs in, then switches users instead of logging out. A Chrome process for every user eats up a lot of RAM. For a few extra bucks, I save everybody in the household tens of minutes per day (my kids are constantly switching users... I should probably get more machines).

Comment Re:Wii U problem is not underpowered. (Score 1) 559

Only one player uses the tablet. The other 4 players use standard Wii remotes.

It actually makes for some interesting game mechanics. Nintendo Land (the game that came with my WiiU) is basically 12 demo games bundled together, and they all do something with the tablet. In Mario Chase, you play hide and seek. The guy with the tablet hides, the guys with the wiimotes seek. The seekers can't see the hider's screen, but they can see each others'. In the Zelda game, the guy with the tablet is an archer, and uses the tablet to look around. The guy(s) with the wiimotes are swordsmen. In the racing game, you steer with the tablet's accelerometers. None of the games are very complicated, but Nintendo Land has replaced Wii Sports as the party game.

I really like Rayman Legends on the WiiU. Some of the levels really make use of the tablet feature, especially in two player mode. The guy with the remote runs the dungeon, and the guy with the tablet uses the touch screen to manipulate the dungeon. It requires a lot of communication between both players, and I think it's really well done. This is the game I point to when people ask why a console needs a tablet. Penny Arcade talked about this game a couple of times, and I agree.

I did end up buying one WiiU Pro controller. All of the functionality of the tablet controller, without a screen. For some of the games my kids play (Transformers), the tablet would always beat the wiimote. The Pro controller restored the balance between the players. It's also more comfortable for long game play than the wiimotes.

TL;DR: I wasn't planning to upgrade to the Wii to a WiiU, but I'm glad I did.

Comment Re:Home server not the fix-all (Score 1) 166

Seconded. I've been doing the same, since 1999. Web spiders are responsible for most of my upstream bandwidth, and I only notice when I'm looking at the log files. None of the 4 ISPs I've had over the years have complained or blocked my service.

The only actual problem I've had is email deliverability. Most destinations would bounce my emails because they came from a Dynamic IP. I configured Postfix to forward everything through Time Warner's mail servers, and I haven't had problems since.

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