Dec 25

The HP Server’s Raid5 Array Data Recovery


Someone has brought me the 4-SAS-disk Hewlett Packard server for data recovery. All the disks have a label saying HP and only a thorough examination shows that these are Seagate disks. A Raid5 array was assembled out of four winchesters. For some time, the device has operated quite well but then two disks fried and the array collapsed.

The HP Server’s Raid5
The HP Server’s Raid5 Array SAS Disks

By the by, the construction of the disk box is extremely lame. The winchesters have no supply of extra cooling so that they get as hot as blazes. No wonder that they have broken down so soon. The only right way of dealing with raid array errors is work with disk images (to be more precise – with copies of the images, not the originals), i.e. logical assembly of the raid. Such an approach will save the data in case of various types of faults. There is always an opportunity to copy the data and try out a different solution.
It goes without saying that before you acquire sector copies of defective HDDs comprising the raid array, you should first get access to the user zone of the winchesters. In this situation, there have been no serious problems with cloning of subquality hard disks. The SMART attributes of both of them possessed exceeded threshold values, which impeded standard disk launch. However, with the winchesters being connected to a special expansion card making it possible to flexibly customize the disk launch settings and startup the SAS storages with no raid arrays required, I have easily managed to get full disk image dumps, passing unreadable sectors. After that, the most interesting part has begun – it is visual analysis of the acquired dumps. On the face of it, the whole process has turned out to be very simple: already after a 15-minute study and some calculations, I have understood where the first and the next blocks are and what sizes they have. According to the results of the troubleshooting, it was not Raid5 but a variety of Raid4 for it looked like three disks alternated as stripe blocks and a parity block on the 5th disk.
However, assembly of the array with the stated parameters has shown that the raid was compiled incorrectly. It is possible to discern two sections and a correct beginning of MFT notes in both of them but most folders are described erroneously in the directory tree or are empty and most files possess an irregular sig.
Further examination was not successful until it dawned upon me that it was an HP server and these servers had a significant feature – it is the so called raid array build delay. What is raid build delay? It is simply a certain shift which results in classic alternation of parity blocks in all the array’s disks in the 5th raid. The next step is to calculate the shift generating Raid5 and when assembling take into account the fact that up to a certain moment this is stripe on 3 disks, parity blocks on the 4th disk, and then a usual backward parity Raid5.

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Dec 06

Tha Past and the Future of the Supercomputer. Historical Review

The beginning of the history of supercomputers is considered 1837, just at that time of Charles Babbige constructed an ancestor of all modern personal computers – Analytical Engine (You can see it in the picture on the left).

Let’s take a brief look at the history of supercomputers and denote the most interesting and significant events associated with this field of information technologies.





1941 Zuse Z3
The first computer, Z3 by name, was designed by the engineer Konrad Tsuze and its size was so large that it looked like a cupboard. It was destroyed during the air raid in 1943.

1964 CDC 6600
Seymour Cray created the first supercomputer whose cost was about $8 million. That machine remained the fastest in the world for a long time.

1976 Cray 1
After setting up his own firm, Cray produced the supercomputer Cray 1 with a capacity of 250 million flops. This model was in a huge success.

1984 M13
One gigaflop was conquered: designed in the USSR the supercomputer M13 worked at a speed of 2.4 billion flops.

1993 TOP 500
Hans Moyer, a Professor from the German city of Mannheim, led the list of the most powerful supercomputers in the world since 1986. In 1993 this list was replaced by rating TOP500.

1995 Nuclear weapons
In the United States Advanced Simulation and Computing project (advanced calculations and simulations program) was launched. Computer simulators replaced real tests of nuclear weapons.

1996 Checkmate
The supercomputer called Deep Blue managed to beat the world chess champion Garry Kasparov in one party out of six. And in 1997 the victory was won already in the whole match.

1997 ASCI Red
A new USA’s breakthrough USA: the performance of ASCI Red developed by Americans exceeded one teraflops.

2008 Petaflops
It took him 11 years to overcome the border of one petaflops. The roadrunner supercomputer from IBM is valued at$ 133 million.

2010 Tianhe-1A
The United States is recognized as a computer superpower, but the Chinese development of Tianhe-1A puts under question the hegemony of the Americans.

2012 Sequoia
The heavy-duty computer Sequoia constructed in the United States works six times faster than Tianhe, and sets a new world record – 16,3 petaflops.

2019 Ekzaflops
Experts predict that by 2019 computers will have been able to process quintillion (18 zeros number) operations per second.

Dec 06

HDD segment is going through a tangible slump in demand

The third quarter of 2012 became unsuccessful for hard disk drives manufacturers. The world’s supply of HDD has decreased by a whopping 11%. Experts IHS iSuppli find the reason for the decline in a whole range of economic and market factors, among which are unstable situation in the world economy, the decline in PC sales and growing popularity of tablets.

For the period from July to September in the world 139,2 million hard drive were sold, as against 157 million in the second quarter of 2012. The decline in the third quarter seems to be particularly sharp in the background of the fact that a quarter earlier 8-percent rise in HDD supply was reported. Also, it is noted that there have never been such low indicators of hard drives supply in this period of the year for at least five years. For example, in the third quarter 2011 175,3 million hard drives were sold.

As regards alignment of forces in the segment, the largest manufacturer of HDD drives is still Western Digital. During the last quarter the company provided 62.5 million hard drives, it is 45% of the total HDD volume. Seagate Technology takes the second place with the result of 57,6 million HDD (41%). Toshiba which traditionally is the third one in this list, has brought 19.1 million hard drives to the world market, or 14% of the total volume.

the same order is characterized for vendors in the revenue ranking: the head of the list is Western Digital – hard disk drives sales have brought 4,03 billion dollars, Seagate is on the second position with the result of 3.75 billion dollars, and Toshiba has got 950 million dollars from HDD sales and takes the third place.

According to IHS iSuppli forcast, in the fourth quarter of 2012 hard drive delivery can be reduced again. However, at this time the decline will be largely connected with the seasonal factor – by the end of the year the market traditionally suffer from a drop of HDD shipments. However, if the situation on the PC market improves, experts expect the beginning of activity in HDD-segment which is most likely to happen in 2013.