[dundee] ELF yourself encryption

[Lee Hughes]

I've been looking at linux raid 1 performance, i.e two driver, mirrored.

Seems that I saw something I was not familiar with 

check dis

  mdadm --create /dev/md2 --chunk=256 -R -l 10 -n 2 -p f2 /dev/sda2 /dev/sdb2

  mkfs -t ext3 /dev/md2

   RAID type      sequential read     random read    sequential write   random write
   Ordinary disk       82                 34                 67                56
   RAID0              155                 80                 97                80
   RAID1               80                 35                 72                55
   RAID10,n2           79                 56                 69                48
   RAID10,f2          150                 79                 70                55


from http://linux-raid.osdl.org/index.php/Performance

but the performance is double? what gives..

I always thought that raid-1 gave a read performance increase?
i.e it would read block in alternative drives?

And raid 10 (mirror+striping), takes 4 drives?

so, what does f2 do, do I get half the disk space?

I can't work this out!






--- On Fri, 19/6/09, lug at seany.us <lug at seany.us> wrote:

From: lug at seany.us <lug at seany.us>
Subject: Re: [dundee] ELF yourself encryption
To: "Tayside Linux User Group" <dundee at lists.lug.org.uk>
Date: Friday, 19 June, 2009, 4:13 PM

I totally agree, software raid is so flexible. I too was stung by the failed controller meaning dataloss.

Linux md raid 1 has about 1% CPU overhead and you can manage it directly via the commandline (no messing around with stupid BIOS screens). With CPU speeds these days software raid can easily compete with hardware raid.

Hardware raid is only really nessesary if you are running something other than RAID1, such as RAID5.

Of course with most hardware raid solutions you do have the benefit of battery backup on the cache at least.

Regards,
Sean McRobbie

----- Original Message -----
From: "Lee Hughes" <toxicnaan at yahoo.co.uk>
To: "Davidson Kris" <Davidson.Kris at gmail.com>, "Tayside Linux User Group" <dundee at lists.lug.org.uk>
Sent: Friday, 19 June, 2009 15:36:40 GMT +00:00 GMT Britain, Ireland, Portugal
Subject: Re: [dundee] ELF yourself encryption


why? 

the testing I've been doing with it , seems pretty stable to me, 

have you had bad vibes with it chris? 

I once had a hardware raid controller fail on me, and I couldn't get a replacement 
board, thus I had to wipe the array, and start all over again! 

so, hardware has it advantages, but software is pretty cool too! 

I bet you could even run it over a network...hmmm.network raid! 




--- On Fri, 19/6/09, Kris Davidson <davidson.kris at gmail.com> wrote: 



From: Kris Davidson <davidson.kris at gmail.com> 
Subject: Re: [dundee] ELF yourself encryption 
To: "Tayside Linux User Group" <dundee at lists.lug.org.uk>, "Lee Hughs" <toxicnaan at yahoo.co.uk> 
Date: Friday, 19 June, 2009, 3:22 PM 


Argh, software raid... Kill it with fire! 

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