PERC3 performance issues

jason andrade jason at
Wed Dec 4 18:29:00 CST 2002

On Wed, 4 Dec 2002, Alexander Lazarevich wrote:

> PE4600
> dual 2.8GHz
> 4GB ram
> PERC3/QC RAID controller
> 10 X 73 GB Maxtor U320 drives

nice config.

> if i configure a single maxtor drive in a RAID 0 configuration, put an
> ext3 filesystem on it, and run some bonnie++ benchmarks, i get 30MB/sec
> writes.

i am assuming you mean if you configure 2 or more drives in RAID0 right ?  a
single drive in raid0 is "JBOD" or a Volume.

> if i configure 8 drives in a RAID 5 configuration on the same exact
> RAID channel (destroy the RAID 0 first), and setup an ext3 filesystem of
> the same size, and run the same exact bonnie++ benchmark, i get 46MB/sec
> write.

that seems about right.  past reports here show that people seem to get
between 35-50Mbyte/sec in write performance on the P3/QC.  have you split
the drives across as many channels as possible ?

> that seems bad. if a single disk can do 30MB/sec, then shouldn't 8 drives
> in a RAID 5 be able to do about 140MB/sec writes? everything is the same
> except the RAID configuration and number of disks.

yes and no.  if the raid controller was powerful enough with all other things
being optimal, then sure.  but the perc3/qc (even though it appears to be
the top end of dell's current raid controller pci selection) tops out at
around that.  does your application specifically need > 46Mbyte/sec write
performance ?

if so, you have a number of alternatives

o multiple perc3/qcs with multiple disk sets with a virtualization layer over
  the top

o software raid, which would easily give you this on your config above

o a third party raid controller using the newer intel 30303 engine - read the
  past threads of this list, a good summary of cards was posted.

o upgrade to a higher performance dell storage solution which is externally
  configured raid such as their fibrechannel stuff. CXXX or whatever.

> anyone have similar problems/complaints?

it's been raised many times before about the performance issues of the PERC2/3
especially in comparison with the software raid performance.  there seems to be
no easy solution for it (e.g firmware upgrade or..) at this point.



P.S i don't speak for dell on this, just my own observations partly based on
    previous list feedback..

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