Gordon Henderson wrote:

On Wed, 21 Dec 2005, Sebastian Kuzminsky wrote:

 

quoted

quoted

But how does the performance for read and write compare?
     

Good question!  I'll post some performance numbers of the RAID-6
configuration when I have it up and running.
   

Post your hardware config too if you don't mind. I have one server with 8
drives and for swap (Which it never does!) I created 2 x 4 disk RAID 6
arrays (same partition on all disks) and gave them to the kernel with
equal priority

Filename                                Type            Size    Used    Priority
/dev/md10                               partition       1991800 0       1
/dev/md11                               partition       1991800 0       1

md10 : active raid6 sdd2[3] sdc2[2] sdb2[1] sda2[0]
     1991808 blocks level 6, 64k chunk, algorithm 2 [4/4] [UUUU]

md11 : active raid6 sdh2[3] sdg2[2] sdf2[1] sde2[0]
     1991808 blocks level 6, 64k chunk, algorithm 2 [4/4] [UUUU]

/dev/md10:
Timing buffered disk reads:  64 MB in  0.66 seconds = 97.28 MB/sec

/dev/md11:
Timing buffered disk reads:  64 MB in  0.95 seconds = 67.59 MB/sec

md10 is an on-board 4-port SII SATA controller, md11 is 2 x 2-port SII
PCI cards. (Server is currently moderately loaded, so results are a bit
lower than usual

Cue the must/must not swap on RAID arguments ;-)

I wouldn't swap on RAID-6... performance is importand, swap is tiny 
compared to disk size. I would go to 2GB partitions and four-way RAID-1, 
since fast swap in seems to make for better "feel" and write is cached 
somewhat.

-- 
bill davidsen [off-list ref]
  CTO TMR Associates, Inc
  Doing interesting things with small computers since 1979