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Re: [vox-tech] Totally inappropriate question (about HP)
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Re: [vox-tech] Totally inappropriate question (about HP)

  • Subject: Re: [vox-tech] Totally inappropriate question (about HP)
  • From: Bill Broadley <bill@math.uMAPScdavis.edu>
  • Date: Tue, 17 Apr 2001 15:42:46 -0700
  • References: 008f01c0c78d$e87fce20$cbabbbcc@a21m

On Tue, Apr 17, 2001 at 05:29:45PM -0500, Jay Strauss wrote:
> Hoping that some HP sys admins may be part of this list.

Heh, a few, I just got hpux 11.11 today.

> I'm running HP UX v11.0.0, using a HP Model 20 disk array.

What kind of machine?  What kind of scsi interface?

> Question: How do I build my volume groups out of only the outer cylinders of
> the disks?  And, do I do it when I'm creating my physical volumes, physical
> volume groups, or my logical volumes?

Why?  Bandwidth for arrays is usually limited by the I/O bus or the 
SCSI bus.  SCSI disks can arbitrary remap sectors for numerous reasons
(hard errors, soft errors, ECC coverage).  Each new disk these days is
good for 30 MB/sec or so.  Get 8 going and your quickly exhausting the
PCI bus, an Ultra 160 Channel, or even main memory bandwidth.

I'd just make a volume of the first 1/4th of the block, the 2nd 1/4th, 3rd
and 4th.  Do some bandwidth tests, if theres a difference then the lower
perf ones are the inside tracks, and the higher perf are the outside.

As long as the array is configured for parallel use of the raid and
not sequential (wierd) it should strip the blocks, the stripsize
is an option during volume creation I believe.

If there is no difference in bandwidth do you care?  I guess you
could be doing some wierd minimizing of head travel for slightly
lower seek times.  Of course the usual method is to add more heads...


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