Follow Slashdot blog updates by subscribing to our blog RSS feed


Forgot your password?

Slashdot videos: Now with more Slashdot!

  • View

  • Discuss

  • Share

We've improved Slashdot's video section; now you can view our video interviews, product close-ups and site visits with all the usual Slashdot options to comment, share, etc. No more walled garden! It's a work in progress -- we hope you'll check it out (Learn more about the recent updates).


Comment: Re:Can we get a real Linux filesystem, please? (Score 1) 210

by belrick (#42299387) Attached to: Denial-of-Service Attack Found In Btrfs File-System

Btrfs, like ZFS and Netapp's WAFL, use a far more efficient copy-on-write strategy that avoids the write penalty.

WAFL doesn't do copy-on-write. Copy-on-write means a write to a block in a file requires the original block to be read, written elsewhere for the snapshot, then the new block written in the original location. That's exactly what WAFL doesn't do. WAFL writes all changed blocks for multiple files in big RAID stripes, updating pointers to current copies and leaving snapshot pointers pointing to old copies of the updated files. Very efficient for writes, but changes almost all reads, random or sequential (within a file) into random reads (within the filesystem) because file blocks get scattered according to write order, not location of the block within the file. That's why they want lots of spindles in an aggregate and they love RAM cache and flash cache.

But since you say that copy-on-write avoids the write penalty I think you know what is does but simply don't know that it isn't copy-on-write.

Comment: Re:Maintenance and prevention are not always the s (Score 2) 185

by belrick (#38183010) Attached to: Can Maintenance Make Data Centers Less Reliable?

After that blunder, I was asked to check on all the cameras servers once a week and make sure I could actually open up and view recordings from days past. This is a preventative action, but not really a maintenance one.

No, it's not preventative. It does nothing to prevent the problem. It detects the problem earlier (before, say, a business user does). That's monitoring. It's proactive, not reactive - perhaps that's what you mean?

Comment: Re:Only in Canada eh? Pity! (Score 1) 277

by belrick (#33948282) Attached to: Scientists Fight Back In Canada

I guess people are worried that our state of the art igloo geometric designs, dogsled aerodymanics and maple syrup chemistry are in danger if poltical decisions are made without the benefit of science. Luckily there are only 78 of us in the whole country. We can probably sort it out in about a fortnight over a few Molson's beers while watching ice hockey.

"Who won the damn gold medals at the last Olympics anyways?"

Ha! You can tell you aren't Canadian because you put the word ice in front of hockey - that's redundant.

Comment: Jolicloud (Score 1) 1348

by belrick (#33933012) Attached to: Desktop Linux Is Dead

I've installed dozens of Linux distributions side-by-side on my various laptops over the years and invariably I would be booting into the Windows OS of the day (XP, skipped Vista, happy with 7). Partly because of need to access some Windows-only software but also a comfort level. Even though 90% of my laptop use is for web/Internet. This coming from someone who spent his PhD doing everything in CDE (and having an Amiga at home).

But then I tried Jolicloud 1.0. It is based on Ubuntu but feels a lot more like the iPhone in presentation. Applications arrayed on a home screen. Application windows maximized with very little OS clutter. Web applications promoted to feel like full apps.

It boots so fast on my SSD Thinkpad X200 Tablet and it feels comfortable. Perhaps this is the Linux Desktop everyone is waiting for?

Of course, I'm waiting for them to rev the Ubuntu base they are working on so the two-point multi-touch and Wacom pen of the X200 Tablet actually work (they work in Ubuntu 10.04 and 10.10, if I recall correctly). That and supporting tethering to my iPhone (both of which work in Windows).

Comment: Re:Eh? (Score 1) 420

by belrick (#33079424) Attached to: Internal Costs Per Gigabyte — What Do You Pay?

A $50 HDD does not store data by itself. How does the data get from the application to the drive? Cases, CPU, RAM. What about fault tolerance (RAID)? What about backup? What about labour? The figures cited include all that. What about speed? 450 GB 15k RPM verses a 1 TB 7200 RPM. What about advanced features (NetApp FlexClone, that allows copies as differentials, or SnapVault and SnapMirror (i.e. remote copy and syncronization)). What about backup (tape library, tape drives, tapes). What about floor space, racking, AC, Power, UPS, PDU?

Do you even realize all the costs that go into a burdened per GB cost? The physical hard drive may be a trivial part of the cost.

Comment: How is it an unfair trade barrier? (Score 1) 115

by belrick (#31349246) Attached to: Google Asks US For WTO Block On China Censorship

Don't local Chinese companies that compete with Google, such as Baidu, have to comply with the same censorship restrictions? For it to be an unfair trade barrier, don't local companies have to be treated differently?

For example, in Canada food products must be labelled in both English and French. A US company with US-produced food goods must use different packaging that complies with this law to import those goods into Canada, or, as is often the case, slap a sticker that meets the minimum requirements of the law. Since the law treats local and imported goods the same, it is not considered an unfair trade barrier. It doesn't matter that it is inconvenient for a US company to have to modify its manufacturing process to accommodate that law.

Note I'm not making any statement about the censorship laws being fair or moral in and of themselves.

Comment: Re:What about write speed? (Score 3, Insightful) 135

by belrick (#30864330) Attached to: IBM Sets Areal Density Record for Magnetic Tape

If the areal density increases uniformly in both directions, then you can expect that the read/write speed goes up by the square root of the areal density increase. That is, for 43.75 you'd expect a speed increase of at least between 6 and 7 times. Note that sometimes the density increase is achieved in only one direction or the other, depending on what technology was used to achieve it, in which case all or none of the density increase results in speed increase.

You can achieve speed increases by using multiple heads. LTO and the 3590/3592 proprietary tape technology on which it is based use 8 or 16 tracks read/written simultaneously, with tracks interleaved. There might be 256 tracks with tracks 1, 17, 33, ..., 241 being accessed, then 2, 18, ..., 242. etc. Doubling the number of tracks (density increase of 2 widthwise) wouldn't increase read/write speed. Doubling the number of tracks while simultaneously doubling the number of heads would.

Note that with 8 or 16 heads spread across the tape width, error correction is achieved by writing a matrix of bits (across the tape as well as down the length) with ECC bits added.

It is the quality rather than the quantity that matters. - Lucius Annaeus Seneca (4 B.C. - A.D. 65)