Nov

27

How to repair Linux(CentOS) software RAID

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Sooner or later hard drives fail…

That’s why we use RAID arrays. The best solution is to use hardware RAID – one assisted with specialized processor on the board. In that category I do not include cheap (called Fake RAID) solutions integrated on the motherboard.

But unfortunately sometimes real RAID controllers are too pricey – here on help comes software RAID.

The good news is that it is included in most of the recent OS. Linux does not make an exception and the software included is really well optimized and even recommended to achieve better performance over Fake RAID.

…

Now in case of failure we are protected, but RAID 1 and 5 will protect the data in case of one drive failure so it is better to replace the failed drive as soon as possible, but on other side you do not want to stop the machine right now.

NOTE: If you have IDE HDD do not use following procedure. IDE drives are NOT HOTSWAPPABLE and removing it may cause MORE DAMAGE.

This is valid also for ordinary s-ATA and SCSI drives.

In case that you have hotswappable drive SCA or similar you can replace the drive when the machine is working.

If you are not sure check the documentation that come with your hardware.

And now after all this precautions let’s start:

Determine the failed drive

To check what array and what drive have problem simply type:

cat /proc/mdstat

Here is sample output:

md2 : active raid5 sdd2[4](F) sda2[0] sdc1[2] sdb2[1]


106221312 blocks level 5, 256k chunk, algorithm 2 [4/3] [UUU_]

In this case the problem is sdd.

Check drive size and type

For the size type:

fdisk -l

And look for sdd in the output.

To check exact drive model type:

dmesg|less

and again look just before SCSI device sdd:

Next step is to obtain replacement drive

(ideally the same model)

Dump the partition table from the drive, if it is still readable:

sfdisk -d /dev/sdd > partitions.sdd

Remove the drive to replace from the array:

mdadm /dev/md2 -r /dev/sdd2

Look up the Host, Channel, ID and Lun of the drive to replace,

by looking in

cat /proc/scsi/scsi

Remove the drive from the bus

echo "scsi remove-single-device 1 0 3 0" > /proc/scsi/scsi

Verify that the drive has been correctly removed

by looking in

cat /proc/scsi/scsi

Physically replace the drive

Unplug the drive from your SCA bay, and insert a new drive
Add the new drive to the bus:

echo "scsi add-single-device 1 0 3 0" > /proc/scsi/scsi

(this should spin up the drive as well)

Recreate the layout

Re-partition the drive using the previously dumped partition table:

sfdisk /dev/sdd < partitions.sdd

If failed drive was unreadable here you need to create new partitions

Add the drive to your array

mdadm /dev/md2 -a /dev/sdd2

You can check if the operation was successful by issuing

cat /proc/mdstat

Inspired with modifications from

Nov

13

First 45-nm CPUs from AMD

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AMD officially announced first Quad Core 45-nm Opteron CPUs code name “Shanghai”.

They are not only up to 35% faster than previous line but also consume 35% less power. In addition improvements in virtualization can increase performance up to 40%.

They use improved Direct Connect Architecture in conjunction with HyperTransport 3.0 and AMD-V including new Rapid Virtualization Indexing feature.

New 45-nm process allowed to increase L3 cache size up to 6M.

Nov

11

newegg comes in Canada…

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newegg leading online retailed for conputer related equipment now expands in Canada.

New site is accessible here:

Nov

9

New version of Sumatra PDF – 0.9.3

Filed Under Windows, news | Leave a Comment

It was a while I did not check the status of the project, but after I opened my application it detected new version and prompted me do I want to update.

So now I have version 0.9.3. Here are the changes made from my last update:

0.9.3 (2008-10-07):

  • fix an issue with opening non-ascii files
  • updated Japanese and Brazilian translation

0.9.2 (2008-10-06):

  • ability to disable auto-update check
  • improved text rendering – should fix problems with overlapping text
  • improved font substitution for fonts not present in PDF file
  • can now open PDF files with non-ASCII names
  • improvements to DDE (contributed by Danilo Roascio)
  • SyncTex improvements
  • improve persistence of state (contributed by Robert Liu)
  • fix crash when pressing ‘Cancel’ when entering a password updated translations

As usual latest version can be downloaded from official web site.

    Nov

    3

    Another “loyal” vendor seeks for alternatives

    Filed Under Linux, news | Leave a Comment

    Microsoft is rushing to release Windows 7…

    After market success of Apple MAC OS X and Asus EeePC using alternative operating systems the ecossytem arround M$ succes is seeking for alternatives.

    BusinessWeek reports that HP is trying to improve Vista or even replace it with another OS  possibly assembled by HP engineers.

    HP has their own HP/UX unix based OS used in their high end servers so probably they will reuse their expertize in that field to release ..ux based OS.

    Sep

    25

    Browser tests part III

    Filed Under Windows, news | Leave a Comment

    Here is the next tests I’ve made on the same machine with same browsers as in the trevious tests. This test is benchmarking java script performance. And here is source of the test. Relusts are:

    Opera

    • Array object 391
    • Date object 63
    • Error handling 46
    • Math object 63
    • RegEx object 219
    • String object 234
    • DOM 172
    • Ajax declarations 156
    • Total Duration 1344

    Firefox

    • Array object  66
    • Date object  42
    • Error handling  89
    • Math object  58
    • RegEx object 191
    • String object 726
    • DOM  269
    • Ajax declarations 378
    • Total Duration  1819

    Chrome

    • Array object 273
    • Date object 213
    • Error handling 8
    • Math object 17
    • RegEx object 67
    • String object 39
    • DOM 55
    • Ajax declarations 413
    • Total Duration 1085

    IE

    • Array object 250
    • Date object 79
    • Error handling 187
    • Math object 203
    • RegEx object 531
    • String object 110
    • DOM 328
    • Ajax declarations 703
    • Total Duration 2391

    Safari

    • Array object 47
    • Date object 78
    • Error handling 219
    • Math object 172
    • RegEx object 125
    • String object 31
    • DOM 47
    • Ajax declarations 156
    • Total Duration 875

    And the verdioct is:

    Safari is the fastest in this test, followed by Chrome, Opera, Firefox and as usual IE is last one.

    Side note: In the tests I’ve remarked that only opera and IE correctly(retained the formatting) copied the data in clipboard.

    Sep

    9

    Browser tests – CSS rendering

    Filed Under Windows, news | Leave a Comment

    After first comparison let’s compare how fast browsers render CSS. We used following file running from local computer:

    css-rendering-benchmark-2500-positioned-divs

    File found here.

    Here are the results:

    • IE – 937ms
    • Opera – 422ms
    • Firefox – 730 ms
    • Chrome – 337ms
    • Safari – 141ms

    The last two varied a lot in the measurements and the value is the one most frequently appeared.

    Comments

    As you can see results are similar to the previous tests. from bottom to top. IE, FF, Opera, Chrome and Safari wins.

    Other tests will follow so subscribe to RSS feed .

    Sep

    7

    Chrome, FF, Opera and IE Acid3 tests

    Filed Under Windows, news | Leave a Comment

    Recently Google announced their own browser called Chrome. It seems pretty fast and promising, but still do you want to give all your information to Google…

    But this post is not privacy related. After having so many browsers on the market probably you wonder which one is the best. Lets do some tests.

    Test

    One of the tests available is ACID available at http://www.acidtests.org/.

    Latest version of the test is ACID3.

    So lets started.

    Participants

    • IE 7
    • FF 3.0.1
    • Safari 3.1.2
    • Opera 9.52
    • Chrome Beta 0.2.149.29

    What will be the testbed?

    All tests are executed on Windows XP SP3

    Results

    Here is the showcase:

    As you can see IE had real problems.
    How the others will do?

    Firefox is doing OK

    Safari is doing really good….

    For now Opera has highest score…

    How Google browser will score?

    Conclusion

    As you can see none of the browsers did not pass ACID3 test. Chrome as Beta is better than FF and Safari, but still behind Opera. As for the other participant IE this was the only browser who did not pass even ACID2 test.

    Aug

    24

    New form of “image” spam

    Filed Under news | Leave a Comment

    Does someone remember those ASCII pictures we used to print on old printers. Like this one:

    db   db d8888b.  .o88b.  .d88b.  .88b  d88.    d888888b d8b   db d88888b  .d88b.
88   88 88  `8D d8P  Y8 .8P  Y8. 88'YbdP`88      `88'   888o  88 88'     .8P  Y8.
88ooo88 88oooY' 8P      88    88 88  88  88       88    88V8o 88 88ooo   88    88
88~~~88 88~~~b. 8b      88    88 88  88  88       88    88 V8o88 88~~~   88    88
88   88 88   8D Y8b  d8 `8b  d8' 88  88  88 db   .88.   88  V888 88      `8b  d8'
YP   YP Y8888P'  `Y88P'  `Y88P'  YP  YP  YP VP Y888888P VP   V8P YP       `Y88P'

    Spammers get more and more creative… and start using this art to trick spam filters.

    Aug

    23

    Sumatra 0.9.1

    Filed Under news | Leave a Comment

    Krzysztof Kowalczyk continue to improve his PDF viewer.

    Shortly after releasing 0.9, 0.9.1 is released for download.

    Here are the improvements from previous version:

    • improved rendering of some PDFs
    • support for links inside PDF file
    • added -restrict and -title cmd-line options (contributed by Matthew Wilcoxson)
    • enabled SyncTex support which mistakenly disabled in 0.9
    • misc fixes and translation updates

    Download it

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