Date: Fri, 29 Apr 2005 16:09:26 +0100 From: "Steven Hartland" <killing@multiplay.co.uk> To: "Brian Candler" <B.Candler@pobox.com> Cc: freebsd-current@freebsd.org Subject: Re: Very low disk performance Highpoint 1820a Message-ID: <0a8401c54ccd$6f346ac0$7f06000a@int.mediasurface.com> References: <069901c54bfd$2967ba40$7f06000a@int.mediasurface.com> <42722CB9.7050702@corp.grupos.com.br> <20050429150057.GA93707@uk.tiscali.com>
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----- Original Message -----
From: "Brian Candler" <B.Candler@pobox.com>
> - try reconfiguring your array as 5 separate disks, and dd from a single
> disk. If it's still slower than your ATA disk, then it's probably SCSI
> transfers or controller I/O bandwidth which are slowing things down.
Was gonna try pulling one of the disks and seeing what the indiviual disk
performance was but considering 3 other controllers from different
manufacturers are all showing the same on 5.x but not on 4.x ( from one
report ) It suggests something more sinister in 5.x
> If you get equal or better performance than your ATA disk, then it becomes
> likely that the RAID configuration is the bottleneck.
Inlikely considering it has 8 SATA 150 channels on 64bit PCI-X @ 133Mhz
> - try reconfiguring your array as two mirrored pairs, and do the same test
> again.
> RAID5 isn't necessarily a good choice for high-performance applications; a
> single block write requires two reads and two writes (to the target data
> disk and the parity disk), and therefore write access to the array is likely
> to be *slower* than to a single disk. You might be better off with
> mirroring. It handles random writes better, and you may get double the
> random read performance since there are two copies of all the data.
Primarly interested in read and considering write performance us 140MB/s
compared with 40MB/s read not really worried about that atm
> RAID5 is acceptable if your application is mostly read-only though (which
> your dd test is, of course)
Thanks for the ideas though :)
Steve
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