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 ================================================ This e.mail is private and confidential between Multiplay (UK) Ltd. and the person or entity to whom it is addressed. In the event of misdirection, the recipient is prohibited from using, copying, printing or otherwise disseminating it or any information contained in it. In the event of misdirection, illegible or incomplete transmission please telephone (023) 8024 3137 or return the E.mail to postmaster@multiplay.co.uk.
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