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The State of ZFS On Linux

MightyYar Re:Unfamiliar (361 comments)

zfs also keeps more data (a lot more) in memory than a "regular" filesystem, so you are more likely to encounter flaky memory in the first place. If I weren't going to use ECC RAM, I would probably forgo these fancy hashing filesystems and instead run something more mundane and then do a separate data integrity check with my backup. I use Unison for my data that is impractical to keep on ZFS. It is slow but has saved my butt on data that is important to me (family photos with some corruption on the master).

2 days ago
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SanDisk Releases 512GB SD Card

MightyYar Re:Fahrenheit? WTHolyF? (204 comments)

Sea water is more abundant than fresh water. There is nothing exact about the point at which "fresh" water freezes. And pure water won't freeze until you give it a nucleation site. Try it in the freezer with deionized or distilled water sometime, it's actually really "cool". :p

2 days ago
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SanDisk Releases 512GB SD Card

MightyYar Re:Fahrenheit? WTHolyF? (204 comments)

I think you are mistaken. The equation converting F to C is linear. F = C * 1.8 + 32.0. Both units are completely arbitrary. F used the freezing point of brine while C used the freezing point of pure water as a zero reference. F used the human body temperature and C used the boiling point of pure water as the 100 reference. Arbitrary.

2 days ago
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SanDisk Releases 512GB SD Card

MightyYar Re:Fahrenheit? WTHolyF? (204 comments)

0 degrees F is the triple point of seawater, which is a lot more common than pure water.

100 degrees F is the human body temperature.

Still having trouble?

2 days ago
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The State of ZFS On Linux

MightyYar Re:Magic (361 comments)

btrfs sounds very interesting. It was not ready for prime time when I setup my current box, which is why I chose zfs instead. I'll have to try to murder it in a VM :)

Can you set btrfs to use arbitrary block devices or files? One of the things that made it easy to screw with zfs was it's ability to do so. I was able to set up a VM and do random writes to the "drives" it was using to see how it would respond. Anyway, to my surprise btrfs seems production-ready at this time so I'll have to play with it.

2 days ago
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The State of ZFS On Linux

MightyYar Re:Magic (361 comments)

When I ran mdadm I would just partition the disks so that I was running multiple raid5s on each drive (so if I had 3x1TB and 2x3TB drives I'd have 6TB of usable space - 4x1TB+1x2TB).

Yes, you can do this with zfs as well, but you need to be very, very careful or you won't have the redundancy that you think you do. There are crazy partition schemes that can let you do Drobo-ish things - but they get so complicated that you need to keep track of them in something like an Excel spreadsheet. :)

Besides, zfs seems to like having the entire drive.

2 days ago
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The State of ZFS On Linux

MightyYar Re:Unfamiliar (361 comments)

I'd love for you to be right, but you haven't added any information to the discussion so it is hard to believe you.

2 days ago
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The State of ZFS On Linux

MightyYar Re:Unfamiliar (361 comments)

Unreliable SATA cables or bad drive electronics can do EXACTLY the same thing.

No, because the corruption will be caught. I - and many others - have had controller failures and bad hard drives cause corruption on the drives, but this corruption was caught during the scrub. If the data is bad in-memory and then hashed and written to disk in that condition, the corruption will be silent.

Even ECC RAM has a finite undetected bit error rate.

ECC RAM will only correct 1 bad bit, but the system is supposed to halt on 2 bad bits. A halt is better than operating in an unknown state, IMHO.

Obviously ECC RAM is a Good Idea when you have Important Data, no matter what the file system is, but there is absolutely nothing magic about ZFS that makes magically higher demands on RAM.

Even if you aren't worried about the specific scenario where the whole pool goes down, taking all the trouble to run a filesystem with parity seems silly if you can't trust the error detection/correction to actually work. And since you are writing a hash as well as a file, you are doubling the opportunities to corrupt any particular file vs a regular file system.

2 days ago
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The State of ZFS On Linux

MightyYar Re:Magic (361 comments)

Not something I would attempt. Personally, I accept this limitation and always add drives in pairs. Upgrading capacity then becomes a 2-drive cost instead of a number_of_disks_in_raid cost.

3 days ago
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The State of ZFS On Linux

MightyYar Re:Magic (361 comments)

then there is no easy way to replace those with 5 3TB drives one at a time and actually get use out of the extra space.

It's not THAT bad. You do this:
1. Put new disk in usb cradle.
2. Run 'zpool replace', swapping new disk for old disk.
3. Take the new disk and physically replace the old disk.
4. Repeat 1-3 for each new disk until you have the whole array running at the new capacity.
5. If autoexpand is not enabled, run the 'zfs online' command with the '-e' flag to use the new capacity.

I've only used FreeBSD, not Linux - but I presume this would work so long as you are giving ZFS the whole disk. ZFS does not care which interface disks are attached to... you can take them all out and shuffle them around and it will map them correctly.

3 days ago
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The State of ZFS On Linux

MightyYar Re:Technobabble... (361 comments)

I've been a member of the Church of Parity ever since I discovered that some of my dutifully backed-up family photos had not only gotten corrupted, but the backup dutifully copied the corruption as well. Ever since, I use backup tools which do a parity check (e.g. Unison) and I try to store important things on ZFS if I can.

In my case I was lucky and I had an older backup without the corruption. But lesson learned... Also, have more than one backup :)

3 days ago
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The State of ZFS On Linux

MightyYar Re:Unfamiliar (361 comments)

ZFS is in the middle, more easily expandable than some, but definitely not as good as the easiest.

Yes, ZFS is not a Drobo. You need to plan out your disk usage from the beginning, because you are kind of stuck with it.

For instance, if you have 5 disks and they are all the same size and you want 2 disk redundancy, it is almost a no-brainer to setup a raidz2. The downside is that if you ever want to make the vdev larger by replacing disks, you need to replace all 5 disks to the new larger size... a vdev is limited by the smallest disk. You can mitigate this by putting the same 5 disks into a pair of mirrors plus a hot spare. You will lose some initial capacity, but then later on you can add capacity by swapping out just two disks or by adding another pair to the pool.

And once you've added a vdev to the pool, you can never remove it... that's probably the biggest irritation for me personally. Even that isn't such a big deal, since it is so easy to clone the whole pool to another one.

3 days ago
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The State of ZFS On Linux

MightyYar Re:Working well for me (361 comments)

If you decide to chance it, make sure you don't use the "scrub" functionality on ZFS. Scrub can cause memory errors to eat your pool like a cancer.

Or, just use ECC :)

3 days ago
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The State of ZFS On Linux

MightyYar Re:License mismatch (361 comments)

There is "free as in beer" (usually both GPL and BSD). There is "free as in freedom" (BSD). And then there is "free as in free-range chickens" (GPL).

3 days ago
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The State of ZFS On Linux

MightyYar Re:Unfamiliar (361 comments)

I would add to you "cons" list that it requires* ECC RAM, though you should probably be using that anyway.

* It's not technically a requirement, but you'll probably be sorry if you don't use it.

3 days ago
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Ask Slashdot: What Smartwatch Apps Could You See Yourself Using?

MightyYar Re:The war that no one wanted (470 comments)

I guess I risk getting into a semantic argument, so I should just stop. From my perspective, the iPod itself never dropped in price but they did add less-capable models at lower price points. You are probably right from your perspective - something with the capabilities of the currently-offered watch will certainly be available at a lower cost, but there will always be a $350-ish model as well.

4 days ago
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SpaceX and Boeing Battle For US Manned Spaceflight Contracts

MightyYar Re:Decisions, Decisions... (123 comments)

I know that Volvos have largely been displaced by the Prius in the, "Oh, God, I'm stuck behind X," department - but I'll never be able to shake the years of conditioning from getting stuck behind some boxy 7xx series floating along at or under the speed limit.

4 days ago

Submissions

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MightyYar MightyYar writes  |  more than 7 years ago

MightyYar (622222) writes "Apparently Al Gore's home energy use has actually increased since he made "An Inconvenient Truth", according to The Tennessee Center for Policy Research. While this organization is certainly not apolitical and I am a bit skeptical about their claims, if true this would give Gore critics further ammunition — he would indeed appear to be an elitist hypocrite, willing to preach to us about how to live without following his own advice. For us geeks, the Drudge Report gives us the numbers."

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