PE6650 Disk I/O performance under Linux

jason andrade jason at
Mon Aug 26 19:46:00 CDT 2002

On Tue, 27 Aug 2002, Norman Gaywood wrote:

> Good questions. We are looking at getting a PE6600 and I've been a bit
> worried about the reports of slow RAID hardware. There also seems to be
> some people recommending software RAID.

there are a few things you could do if you are worried about this.  i've
put them in rough order of cost (increasing down the list) and preference
(also i guess increasing down the list)

o look at software raid.  this is my least preferred solution but it
  might be advisable if you need screaming I/O and you don't have an
  application that needs cpu at the same time.  my least preferred
  solution but it has worked very well for some other list members and
  if properly installed/configured it "just works". (heh)

o look at replacing the DC card with a QC, even if you don't use all the
  channels.  from various reports, the QC engine seems to be signficiantly
  better, especially for writes.

o put in a third party raid card and connect your dell storage to it.  not
  supported by dell i guess, so weigh up your options.

o look at third party storage and connect it to your system using a standard
  HBA (e.g a U160 or even U320 scsi card).  again, not supported by dell.
  the third party storage might do the hardware raid "in chassis" rather than
  on a card.

o look at fibrechannel attach instead (e.g dellemc FC4500) and doing the raid in
  hardware (not on the HBA).  extremely good performance can be had here.

o look at a SAN environment instead of direct attach fibrechannel for servers.

lastly, try and make sure memory is not a bottleneck in any servers.  this seems
to be unlikely in what people have reported, but it's worth noting.



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