Re: Best suiting OS

[Karl Denninger <karl@xxxxxxxxxxxxx>]

Scott Carey wrote:

On 10/3/09 7:35 PM, "Karl Denninger" <karl@xxxxxxxxxxxxx> wrote:
 
  

I am a particular fan of FreeBSD, and in some benchmarking I did between it
and CentOS FreeBSD 7.x literally wiped the floor with the CentOS release I
tried on IDENTICAL hardware.
I also like the 3ware raid coprocessors - they work well, are fast, and I've
had zero trouble with them.

-- Karl
    

With CentOS 5.x, I have to do quite a bit of tuning to get it to perform
well.  I often get almost 2x the performance after tuning.

For I/O --
Deadline scheduler + reasonably large block device read-ahead + XFS
configured with large 'allocsize' settings (8MB to 80MB) make a huge
difference.

Furthermore, the 3ware 35xx and 36xx (I think) I tried performed
particularly badly out of the box without tuning on CentOS.

So, Identical hardware or not, both have to be tuned well to really compare
anyway.

However, I have certainly seen some inefficiencies with Linux and large use
of shared memory -- and I wouldn't be surprised if these problems don't
exist on FreeBSD or OpenSolaris.
  

I don't run the 3x series 3ware boards.  If I recall correctly they're not true coprocessor boards and rely on the host CPU.  Those are always going to be a lose compared to a true coprocessor with dedicated cache memory on the card.

The 9xxx series boards are, and are extremely fast (make sure you install the battery backup or run on a UPS, set the appropriate flags, and take your chances - writeback caching makes a HUGE difference.)

Other than pinning shared memory on FreeBSD (and increasing a couple of boot-time tunables to permit large enough shared segments and semaphore lists) little is required to get excellent performance.

The LSI cards that DELL, Intel and a few others have used (these appear to be deprecated now as it looks like LSI bought 3ware) also work well but their user interface is somewhat of a pain in the butt compared to 3Ware's.

-- Karl

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