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Displaying posts with tag: RAM (reset)

Faulty Physical Ram
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Some times it's very difficult to find out exact issue. Specially When it's related with hardware. Similar scenario, i faced with a client. I have been provided with a new box to setup mysql server. After setup mysql along with other application, mysql frequently goes down without any comment in mysql error log file. Spending few days verifying os, logs, mysql and later i found the culprit using memtester tool. Thanks to memtester tool.
[root@voice ~]# memtester 5 1
memtester version 4.1.2 (32-bit)
Copyright (C) 2009 Charles Cazabon.
Licensed under the GNU General Public License version 2 (only).

pagesize is 4096
pagesizemask is 0xfffff000
want 5MB (5242880 bytes)
got  5MB (5242880 bytes), trying mlock ...locked.
Loop 1/1:
Stuck Address       : ok      
Random Value        : ok
Compare XOR         : ok
Compare SUB         : ok
FAILURE: 0x7888cfc4 != 0xe088cfc4 at
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RAM flakier than expected
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Ref: Google: Computer memory flakier than expected (CNET DeepTech, Stephen Shankland)

Summary: According to tests at Google, it appears that today’s RAM modules have several thousand errors a year, which would be correctable if it weren’t for the fact that most of us aren’t using ECC RAM.

Previous research, such as some data from a 300-computer cluster, showed that memory modules had correctable error rates of 200 to 5,000 failures per billion hours of operation. Google, though, found the rate much higher: 25,000 to 75,000 failures per billion hours.

This is quite relevant for database servers because they write a lot rather than mainly read (desktop use). In the MySQL context, if a bit gets flipped in RAM, your data could get corrupted, or

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MySQL and the Linux swap problem
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Ever since Peter over at Percona wrote about MySQL and swap, I’ve been meaning to write this post. But after I saw Dathan Pattishall’s post on the subject, I knew I’d better actually do it.

There’s a nasty problem with Linux 2.6 even when you have a ton of RAM. No matter what you do, including setting /proc/sys/vm/swappiness = 0, your OS is going to prefer swapping stuff out rather than freeing up system cache. On a single-use machine, where the application is better at utilizing RAM than the system is, this is incredibly

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Showing entries 1 to 3

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