Two big things can affect RAID-5 performance: 1. Battery backup. If you don't have a working battery attached to the card, it will turn off the write-back cache, no matter what you do. Check this. If you're unsure, use the mfiutil tool that I added to FreeBSD a few months ago and send me the output. 2. Partition alignment. If you're using classic MBR slices, everything gets misaligned by 63 sectors, making it impossible for the controller to optimize both reads and writes. If the array is used for secondary storage, simply don't use an MBR scheme. If it's used for primary storage, try using GPT instead and setting up your partitions so that they are aligned to large power-of-2 boundaries. Scott On Jun 18, 2010, at 6:27 PM, oizs wrote: > Im using the Samsung F3 disks, which can do 140MB/s sequentially. I have tried different raids raid0 will do just as bad as raid5. I even tried one disk which performed as expected 100MB/s+ reads and writes so I'm not sure anymore what could be the problem. Maybe the controller hates samsung disks? > > -zsozso > > On 2010.06.19. 0:21, krad wrote: >> On 18 June 2010 10:08, oizs<oizs_at_freemail.hu> wrote: >> >> >>> I've seen people with the same configuration doing 160MB/s writes and >>> 250MB/s+ reads with raid5 so I still think something isn't right. And using >>> raid10 with 4 disks is a rather large waste of capacity. >>> >>> -zsozso >>> >>> >>> On 2010.06.18. 1:55, Chuck Swiger wrote: >>> >>> >>>> On Jun 17, 2010, at 4:50 PM, oizs wrote: >>>> >>>> >>>> >>>>> I've bought a Dell Perc 5/i because I couldn't make the onboard marvell >>>>> 88sx7042 work with 8.0/8.1 or current, but as lucky as I am, the best I can >>>>> do with 4x1.5tb samsung in raid5 is 60MB/s writes and 90MB/s reads, with >>>>> bbu/write-back/adaptive-read-ahead. >>>>> >>>>> I was expecting at least twice of that, and I'm not sure what can I do to >>>>> get that speed. (I've read man 7 tuning with no success) >>>>> >>>>> >>>>> >>>> Switch to using RAID-10 rather than RAID-5. It's normal for RAID-5 to >>>> have worse write performance than that of a single drive. >>>> >>>> Regards, >>>> >>>> >>>> >>> _______________________________________________ >>> freebsd-current_at_freebsd.org mailing list >>> http://lists.freebsd.org/mailman/listinfo/freebsd-current >>> To unsubscribe, send any mail to "freebsd-current-unsubscribe_at_freebsd.org" >>> >>> >> what are your drives though? Are they SATA green/eco type drives or proper >> SAS enterprise ones >> _______________________________________________ >> freebsd-current_at_freebsd.org mailing list >> http://lists.freebsd.org/mailman/listinfo/freebsd-current >> To unsubscribe, send any mail to "freebsd-current-unsubscribe_at_freebsd.org" >> >> >> > _______________________________________________ > freebsd-current_at_freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-current > To unsubscribe, send any mail to "freebsd-current-unsubscribe_at_freebsd.org"Received on Sun Jun 20 2010 - 00:53:40 UTC
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