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[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[Read more...]
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
[Read more...]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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