RAID Level 55

[Nikolas Britton]

On 7/16/05, Chuck Swiger <cswiger at mac.com> wrote:
> Nikolas Britton wrote:
> > I was reading on wikipedia about RAIDs trying to pass the time and I
> > was thinking why not have RAID 5+5 or 5+5+5 levels, sure you waste
> > 2/3th's of your space but wouldn't this be a killer setup for a
> > directory server where fast reads are of the utmost importance?
> 
> Actually, no.  RAID-5 prioritizes cost and reliability at the expense of
> performance.  RAID-5 does adequate for read-mostly volumes with big files, and
> does worst with lots of writes to small files.

Ok then, a public FTP server... It doesn't matter, when your have a
405,000 RPM drive (27 drives * 15k rpm) you can do just about
anything, but it would excel for data reads and especially random data
reads.

> 
> RAID-5,0 or -1,0 would be a much better choice.
> 
> > Would you add up the transfer rates for each drive to get the total
> > transfer rate of the array?, if true you could easily saturate a 10
> > gigabit ethernet connection with a 555 array of IDE or SATA drives.
> 
> Nope.  Most machines are limited by their PCI bus and chipset to less than
> 1Gb/s of backplace bandwidth, although the higher-end boxes with multiple PCI
> busses or PCIe will do better.

Yes I realize that the PCI bus is limited to a maximum of 260MB/s
(32-bit @ 66MHz) but PCI-X @ 133MHz is 1060MB/s....  Anyways...

I was just thinking out loud if there would be a useful purpose for
this type of RAID array, I was bored because I had to wait for
ethereal to build and then I had to wait till 3am, to do something,
before I could go to sleep for the night.