Software raid rules!

Ard van Breemen ard at telegraafnet.nl
Thu Apr 25 12:19:01 CDT 2002


On Thu, Apr 18, 2002 at 11:28:00AM +0200, Sigbjorn Strommen wrote:
> H A L L E L U J A H! 
> 
> The performance is so much better I can hardly believe it!  (I got
> block read speeds of from 150-170MB/s!) The numbers were so good
> that I did a rerun of all the tests, doubling the data size to 4GB,
> as the server has 1GB RAM, and then I got block reads of about
> 125-148MB/s
Welcome to the club of software raid users.
Did you also notice that your system suddenly gets stable, and
suddenly has a much *LOWER* load?
We have decided -after loosing a lot of money and time on megaraid
cards- that we only use software raid.
Software raid gives us:
- Speed: suddenly the load of the machine decreases because the
  database server is suddenly able to give answers.
- Stability: No weird crashes, no weird and evil raid firware
  upgrades, no nothing, just plain stable.
- Comprehensibility: we understand what is on the disk (we know the
  data structures on the disk, because we have the source).
  Eh, that is, we had an array "out-of-sync" one time, which we tried
  to resolve using dd. After we resolved it, there seemed to be
  plenty of utilities we could have used.
- Ease of operation: No weird management utilities. Worse: We (that is
  a former colleague of me and I on a former job) needed to write
  those management utilities ourselves for the megaraid card, and had
  to sign an NDA. Just to be able to write a megaraid manager that
  can be run from the command line, and was able to do things (like
  initializing an array) without rebooting. And then you have this
  cool utility that only megaraid owners could use and you are not
  allowed to distribute it, grrr.

In my opinion: harware raid as a pci-card is dead. It is expensive,
buggy, slow and unmanagable.

Of course I can see a feature in save NAS or SAN devices where each
unit is controlled by linux with software raid :).
-- 
<ard at telegraafnet.nl> Telegraaf Elektronische Media  http://wwwijzer.nl
Real geeks don't need DNS.




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