external raid arrays

Velocet math at velocet.ca
Thu Feb 21 16:16:16 EST 2002


On Thu, Feb 21, 2002 at 07:45:20PM +0100, Jakob Østergaard's all...
> On Thu, Feb 21, 2002 at 10:53:43AM -0600, Chris Black wrote:
> > We are looking for an external RAID solution that will provide at LEAST 
> > 100MB/s read bandwidth, probably under RAID 10 (0+1). So far I have been 
> > disappointed with performance for external raid arrays that we have 
> > looked into, and I haven't found a good site with actual benchmarks 
> > for external raid arrays. So I'm using the list :)
> > I know some of you probably have some experience in high performance 
> > external raid solutions so I'm asking for tips, suggestions, links, etc.
> > I don't care if it is an Ultra160 connect or fibre channel, but I have 
> > no experience with fibre channel and don't know about compatible cards 
> > with linux.
> > Our budget isn't quite in the EMC range, but I still figure there is 
> > something out there that someone on this list might know about.
> > All replies appreciated. Thanks in advance!
> 
> How much space do you need ?
> 
> Why not simply mocking 12 SCSI disks in an internal enclosure, using
> four LVD Ultra80/160 adapters, running RAID 0+1 over that ?
> 
> You could use Software RAID for good performance, all you'd need to do would be
> to get a motherboard which has more than one PCI bus (133MB/sec marketing
> bandwidth is a little close to 100 MB/sec).

I usually get yelled at for suggesting using md (linux) or vinum (freebsd)
for RAID by other people in similar circles. I expected the same on this
list, so I actually erased the post I was half way through writing about
our experiences. :( But I guess I'll post it now.

We get 54Mb/s read and 44Mb/s write with raid 0+1 on 10Krpm IBM LVD 160
drives with 1 controller. I would expect, with suitably fast CPUs (ours
is a Tbird 900) and 66/64 pci slots with some nice Tekram (we swear by
these) or Adaptec controllers that 4 of them with 12 10Krpm drives would
probably easily net you over 100MB/s read and write.

We've had excellent success with vinum on freebsd for the last 4 years in
our production environments here for servers, and we had an incredibly
harrowing horrible 27 hours of no sleep trying to deal with one massive
AMI MegaRaid BIOS firmware bug a few years ago which took down our hardware
raid array. We went software since then and have had few problems.

/kc
 
> Upsides:  Cheap controllers, standard cabling, simplicity.
> Downsides: Max. 12m cable length (AFAIR),  get's compilcated with *many* disks
> 
> This solution would be pretty much lower than anything rhyming with EMC,
> but please tell us more about what you need.
> 
> -- 
> ................................................................
> :   jakob at unthought.net   : And I see the elder races,         :
> :.........................: putrid forms of man                :
> :   Jakob Østergaard      : See him rise and claim the earth,  :
> :        OZ9ABN           : his downfall is at hand.           :
> :.........................:............{Konkhra}...............:
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-- 
Ken Chase, math at velocet.ca  *  Velocet Communications Inc.  *  Toronto, CANADA 
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