Ralf Gross schrieb:
> Peter Grandi schrieb:
> > Ralf> Hi, we have a new large raid array, the shelf has 48 disks,
> > Ralf> the max. amount of disks in a single raid 5 set is 16.
> > Too bad about that petty limitation ;-).
> Yeah, I prefer 24x RAID 5 without spare. Why waste so much space ;)
> After talking to the people that own the data and wanted to use as
> much as possible space of the device, we'll start with four 12/11
> disk RAID 6 volumes (47 disk + 1 spare). That's ~12% less space than
> before with five RAID 5 volumes. I think this is a good compromise
> between safety and max. usable disk space.
Ok, the init of the new 12 disk RAID 6 volume is complete. The
numbers I get now are a bit dissapointing: ~210 MB/s for read and ~110
MB/s for write.
I know that RAID 6 is slower than RAID 5, and that less data disks (10
instead of 15) also slow things down. But 390 MB/s read performance
compared to 220 MB/s is a bit suprising. Particularly because the RAID
5 read performance was limited by the FC (I think). I thought I still
would get 1/3 of the RAID 5 read throughput because of the 5 fewer
disks of the RAID 6. I have to test this again with a larger chunk
size (256k), we'll how much this affects read/write performance.