Mailinglist Archive: opensuse (1420 mails)

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Re: [opensuse] Re: Where does LVM Info live
On 01/20/2014 07:40 PM, Joachim Schrod wrote:
Using (Software) RAID-1 on all my disks was several times the
reason that I could continue my work and prepare for disk exchange
at leisure, instead of stumbling into re-imaging new disks and
missing project dates. I couldn't imagine to live without it. Disks
are cheap, my work time is expensive.


Indeed.
The idea behind RAID-5 was right, it was just done wrong. Hamming coding can add the overlapping check bits to allow an indefinite number of errors to be detected and corrected. We already do that quite transparently in ECC memory.

See http://en.wikipedia.org/wiki/Hamming_%287,4%29_code for one illustration.

So you get to the point where adding drives to carry the data/parity interleaving introduces a higher failure rate .... you know the rest.

RAID-1? Mirroring? So long as you can respond when one drive fails, replace it and rebuild before the other fails ...

Which gets back to LVM...

There have been observations about how its easier to put LVM on top of RAID to to manage the file systems, but why not use the LVM ability to mirror as a form or RAID-1.

It seems that with LVM you can alter add a drive and start mirroring all or only some file systems....


Pro and Con:
-----------

** Do check the dates on these as some information may be out of date **

Possibly out of date:
http://stackoverflow.com/questions/237434/are-raid-and-lvm-mutually-exclusive-and-which-should-i-prefer

This reminds me of my experience with AIX
http://www.olearycomputers.com/ll/linux_mirrors.html

LVM2 mirror faster than RAID
http://www.joshbryan.com/blog/2008/01/02/lvm2-mirrors-vs-md-raid-1/


http://utcc.utoronto.ca/~cks/space/blog/linux/LVMMirroringTemptation
and
http://utcc.utoronto.ca/~cks/space/blog/linux/LVMCautiousMigration
Does anyone have experience with LVM Mirroring?

https://www.centos.org/docs/5/html/Cluster_Logical_Volume_Manager/mirrored_volumes.html

This leads me to think that it might be useful to have a small, possibly SSD, disk for 'the system' to boot from and to hold the log file, and use the "mirrored" system for "data"
http://unix.stackexchange.com/questions/24666/what-does-a-mirrorlog-do-in-lvm-mirroring





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