11-15-2010, 08:15 AM
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Web Hosting Guru
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Join Date: Jan 2004
Posts: 347
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did I just kill my server witht this command ?!?
Ok I'm running centos 5 x64 and doing some testing on new servers that just had all software installed.
I was reading a topic somewhere and someone mentioned this command that they used to test the speed of their hdd raid:
dd if=/dev/zero of=/dev/sda bs=1M count=1000
So I thought that cant do no harm if someone else is running it so I ran it (except I did it with count=10000 because with 1000 it finished too quick as its a 15k SAS RAID10)
Anyway, so a little while later I goto the dc and connect to this server to run some tests, one of them being "arcconf getconfig 1" to retrieve details about the raid...
It doesnt react ... so I run it again .. nothing. Then suddenly it says can't open some log file in /var/log and still doesn't run (I was able to open the same file myself using pico without problems)
So I goto cli and "shutdown -r now" and BOOOM tons of errors all over the screen incl. ext3 related stuff. After a few mninutes of pages and pages of errors, I power off/on the box and it comes back. I enter the adaptec bios and it shows the array as "Optimal" but then when I goto boot ... nothing, doesnt recognize the boot media.
So I run linux rescue from the centos cd and it tells me that that partition table is UNREADABLE and that the only thing it can do is re-initialize the drives causing loss of all data.
Apologies for the long description I just wanted to be detailed.
Anyway, so here I am ..reinstalling centos on this box. Now I want to know if the command that I ran above would/could have caused damage to the partition table or if its more likely to be a hardware (raid controller) problem ????
Scary thing is I ran the SAME command on 5 other IDENTICAL servers and they all seem ok (so far) but I havent tried rebooting them yet
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11-15-2010, 08:27 AM
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Web Hosting Guru
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Join Date: Jan 2004
Posts: 347
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yep looks like I've killed them sll ... just rebooted snother one snd ssme issue, partition table ****ed.
Wow, what A DOUCHE. I feel like such a spastic now.
You'd think after 10 years in the biz I'd know better than to simply run a command like that without first making 100% sure it can do damage.
Oh well 2 days of work lost. But I'm happy believe it or not. It's just software and I can reinstall that easily since these boxes are not live yet... I was worried it was the RAID controller that ****ed up (due to some previous issues with it in relation to its BIOS). Happy to know the raid controller didnt do anything wrong 
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11-15-2010, 08:57 AM
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Aspiring Evangelist
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Join Date: Aug 2002
Location: Milton Keynes
Posts: 352
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Oh this is too funny.
I guess we live and learn Care to name & shame where this 'advice' came from?
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11-15-2010, 09:06 AM
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Newbie
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Join Date: Sep 2007
Posts: 10
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Ouch.... Sounds like one of those days. Good thing it's nothing serious other than the software
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11-15-2010, 09:09 AM
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Web Hosting Guru
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Join Date: Jan 2004
Posts: 347
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wasn't advice really ..just someone mentioning they used that to test the speed of their HDDs (think it was one of those "vibrating fans killed my hdd" threads
but yeah ... its friggin insane and funny at the same time. But I am REEEALLL happy it wasnt the controller that did something as my initial assumption was and I was already starting to consider which controller to replace it with and how much of a huge hassle that is going to be
as it stands its just a bunch of os/cpanel reinstalls ... pain in the arse but I AM in the process of stress testing these boxes before they go live at the end of the month, so this is kinda giving them a bit of a workout.
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11-15-2010, 10:24 AM
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Web Hosting Master
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Join Date: Jan 2001
Location: Miami, FL
Posts: 1,024
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really...
hdparm for the win...
i use dd responsible though....
sorry to hear that you killed your box....
i hope u were able to sleuth out the data.
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11-15-2010, 02:34 PM
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Web Hosting Master
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Join Date: Oct 2009
Posts: 677
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Heh, well.. you could indeed use that command to test the sequential write speed of a RAID. But it would be a destructive test, essentially zero-filling the first 10GB of the disk.
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Your faithful student,
Twilight Sparkle
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11-15-2010, 02:54 PM
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Stairway To Hosting
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Join Date: Mar 2003
Location: Canada
Posts: 8,060
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Ugh. Sounds like someone trolled you... next time, if you're not 100% sure what the command does, don't run it as root. :]
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11-15-2010, 03:14 PM
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That's all it takes?
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Join Date: Aug 2001
Location: Canada
Posts: 2,091
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Quote:
Originally Posted by papi
dd if=/dev/zero of=/dev/sda bs=1M count=10000
Scary thing is I ran the SAME command on 5 other IDENTICAL servers and they all seem ok (so far) but I havent tried rebooting them yet
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I really hope those are not production servers; you overwrite the first 10GB of raw data... those 5 servers should be toast as well. sorry 
if = input
of = output
bs = blocksize
count = count
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11-15-2010, 03:50 PM
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Junior Guru
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Join Date: Mar 2009
Location: deep blue yonder
Posts: 176
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On the off change you're still keen on running the test, replace the original of= with of=foofile and you should be good to go. Remember to remove the foofile when you're done.
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424 bits were harmed in the making of this signature.
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11-15-2010, 05:32 PM
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Web Hosting Master
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Join Date: Aug 2003
Posts: 1,999
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That is pretty amusing. Lesson learned. When I was a newbie I once did yum uninstall libstdc++. That caused one helluva night.
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11-15-2010, 07:14 PM
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Junior Guru Wannabe
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Join Date: Feb 2010
Location: Ohio, USA
Posts: 89
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Nice.
Hope proper backups were kept ; )
__________________
error mounting /proc: No such file or directory
error mounting /sys: No such file or directory
Kernel panic - not syncing: Attempted to kill init!
..OMG they tried to kill init.. you b@stards.
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11-15-2010, 08:19 PM
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Web Hosting Guru
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Join Date: Jan 2004
Posts: 347
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no backups, these were not live boxes!
I'm surprised no one asked yet what ths epeed result was anyway ... 770 megajigabytespersec!! Haha 
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11-15-2010, 10:36 PM
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Junior Guru Wannabe
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Join Date: Feb 2010
Location: Ohio, USA
Posts: 89
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Quote:
Originally Posted by papi
I'm surprised no one asked yet what ths epeed result was anyway ... 770 megajigabytespersec!! Haha |
Nah the zeroing over of your disk is far more amusing than any speed result. 
__________________
error mounting /proc: No such file or directory
error mounting /sys: No such file or directory
Kernel panic - not syncing: Attempted to kill init!
..OMG they tried to kill init.. you b@stards.
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11-15-2010, 11:27 PM
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Web Hosting Master
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Join Date: Jun 2004
Location: Oregon
Posts: 1,147
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Quote:
Originally Posted by papi
no backups, these were not live boxes!
I'm surprised no one asked yet what ths epeed result was anyway ... 770 megajigabytespersec!! Haha |
that test uses buffer, so it's not accurate at all.
if you want to test the real disk speed, you should use dd with oflag=dsync.
so you basically killed your OS by running a not accurate speed test
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