Nick Crane’s Britannia and Floating Islands in Snowdonia, Wales

Watched the first episode of Nick Crane’s Britannia, about England and Wales, and was interested to see a section about Snowdonia which implied that William Camden, the Elizabethan author of the original Britannia, had said that there were was a lake there which had a floating island in it. It implied that Camden would have come across this story by talking to cattle farmers of the area on his travels through North Wales. But that doesn’t seem to be the case at all, in fact the English translation of Camden’s own text says:

Neverthelesse, so ranke are they with grasse that it is a very comon speech among the Welsh, that the mountaines Eriry will yeeld sufficient pasture for all the cattaile in Wales, if they were put upon them together. Concerning the two Meare [lakes] on the toppe of these, in the one of which floteth a wandering Island, and in the other is found great store of fishes, but having all of them but one eye apeece, I will say nothing lest I might seeme to foster fables, although some, confident upon the authority of Giraldus, have beleeved it for a verity.

In other words he was just quoting Giraldus Cambrensis who, in his “The Description of Wales” (1194 CE), wrote:

the latter of which are said to be of so great an extent, that if all the herds in Wales were collected together, they would supply them with pasture for a considerable time. Upon them are two lakes, one of which has a floating island; and the other contains fish having only one eye, as we have related in our Itinerary.

Even then Giraldus is just summarising what he wrote in his “The Itinerary of Archbishop Baldwin through Wales” (1188 CE), where he says:

On the highest parts of these mountains are two lakes worthy of admiration. The one has a floating island in it, which is often driven from one side to the other by the force of the winds; and the shepherds behold with astonishment their cattle, whilst feeding, carried to the distant parts of the lake. A part of the bank naturally bound together by the roots of willows and other shrubs may have been broken off, and increased by the alluvion of the earth from the shore; and being continually agitated by the winds, which in so elevated a situation blow with great violence, it cannot reunite itself firmly with the banks. The other lake is noted for a wonderful and singular miracle. It contains three sorts of fish – eels, trout, and perch, all of which have only one eye, the left being wanting; but if the curious reader should demand of me the explanation of so extraordinary a circumstance, I cannot presume to satisfy him.

So sadly it appears that William Camden was just referring back to a text that was almost 400 years old when the first edition of Britannia was published in 1586.

SSD Drive Using Compression Internally ?

The most excellent Joe Landman has a blog post looking at the performance of an anonymous SSD with a Sandforce SF-1200 controller chipset on it, and comes up with some very interesting benchmark results. But first he comes up with a nice way of quantifying the distance between benchmark results and real life:

I need to understand how close the marketing numbers are to the actual numbers. We need to establish a ratio for this. Call this the Benchmark Significance Ratio, or BS Ratio for short. Define BS Ratio as:

BS Ratio = (what they claim) / (what you measure)

A BS Ratio close to 1 is good. A BS Ratio much greater than 1 is bad. Of course, a BS Ratio much less than 1 is either an indicator of a failed test, or an accidentally released product.

What Joe finds is that the performance of the SSD, in terms of basic things like read/write speed, depends on what you write to it. If you write lots of zeros you find the performance is almost 4 times as much as if you write random data to it. Now as Joe rightly points out, this smacks of compression somewhere in the path between the program and the disk which means that most of the benchmarks you see/do (unless they/you, as Joe does, take care to use random data) will be pretty much meaningless unless you plan to just store zeros. Mind you if you do plan to just store zeros then I suggest just using /dev/null for writing to and /dev/zero to read from – they will give you much better speed and far better capacity for free! πŸ™‚

What intrigues me though is not so much the speed difference but what that means for the capacity of the device – does it claim to be a X GB device but actually store Y GB (where Y > X dependent on compressibility of data) or does it enforce the amount that it can store to the quoted capacity ? Even worse, does the stated X GB capacity depend on your data being compressible and more random data results in less space ? I think the last can be ruled out because I can’t see a way how you would fake that failure to the SATA layers unless you returned failed writes which could cause chaos, especially in a RAID environment. I also suspect that it must enforce a fixed limit as I presume they must fake some characteristics of a spinning disk (heads, etc) for compatibility.

Which is a real shame because you’ve actually got a storage device that could (given the right sort of data) store far more than its stated capacity, if only you could address it in a non-spinning disk like manner. This echo’s other issues with SSD FTL’s like bad wear levelling implementations, etc, which would go away if we had an open interface into the device exposing the internals, that way you could (with this controller) get extra storage for free and potentially even a better wear levelling system into the bargain.

I guess even if that were available I don’t know if filesystems could cope with that (yet), but I wouldn’t mind betting they’d be up for it!

Geeks versus Lawyers, or, China versus the US

Interesting take on why China may well dominate technology in the near future at BusinessWeek:

In China, eight of the nine members of the Standing Committee of the Political Bureau, including the Chinese president, Hu Jintao, have engineering degrees; one has a degree in geology.

Contrast that with the US:

Of the 15 U.S. cabinet members, six have law degrees. Only one cabinet member has a hard-science degree — Secretary of Energy Steven Chu, who won the Nobel Prize in physics in 1997, has a doctorate in physics. President Barack Obama and Vice President Joe Biden have law degrees.

Basically it comes down to political will and understanding on the part of the people with the power.

(Via the ever excellent InsideHPC)

New Records for Global Temperatures (from NOAA)

Two interesting statistics from the NOAA National Climate Data Center:

June 2010 was the fourth consecutive warmest month on record (March, April, and May 2010 were also the warmest on record). This was the 304th consecutive month with a global temperature above the 20th century average. The last month with below-average temperature was February 1985.

and:

It was the warmest JanuaryΓ’β‚¬β€œJune on record for the global land and ocean temperature. The worldwide land on average had its second warmest JanuaryΓ’β‚¬β€œJune, behind 2007. The worldwide averaged ocean temperature was the second warmest JanuaryΓ’β‚¬β€œJune, behind 1998.

Yes, those figures are for the whole planet.

RHEL 6 Betas Drop Xen as Dom0 Host

For folks who’ve not yet noticed, the long foreshadowed dropping of Xen from RHEL6 for anything other than as a guest OS is still on:

Red Hat Enterprise Linux 6 Beta is supported as a Xen guest for the x86 and x86_64 architectures. Additionally, Red Hat Enterprise Linux 6 Beta can be used as both a Xen paravirtualized (PV) guest or as a Fully virtualized (FV) guest with PV drivers. Due to paravirtualized operations (pv-ops) being included in the kernel, the same kernel can be used for either mode of operation as well as for bare metal. There is no support for using Red Hat Enterprise Linux 6 Beta as a Xen host.

If you are using Xen with RHEL as the base for your virtualisation you’ll be wanting to look for alternatives..