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Message-ID: <20080326090527.42286e8e@galadriel.home> Date: Wed, 26 Mar 2008 09:05:27 +0100 From: Emmanuel Florac <eflorac@...ellique.com> To: Bill Davidsen <davidsen@....com> Cc: Chris Snook <csnook@...hat.com>, linux-kernel@...r.kernel.org Subject: Re: RAID-1 performance under 2.4 and 2.6 Le Tue, 25 Mar 2008 19:42:28 -0400 vous écriviez: > And this is what I was saying earlier, there is a trend to blame the > benchmark when in fact the same benchmark runs well on 2.4. As I mentioned, it looks like 2.4 actually buffers write data on RAID-1 which is inherently bad (after all if I do RAID-1 it's for the sake of data integrity, and write caching just counters that). However, how bad dd may be, it reflects broadly my problem : on small systems using software RAID, IO is overall way better with 2.4 than 2.6, especially NFS thruput. Though I can substantially enhance 2.6 performance through tweaking (playing with read ahead, disk queue length etc), it still lags behind 2.4 with defaults settings by a clear margin (10% or more). This isn't true - fortunately - of larger systems with 12, 24, 48 disks drives, hardware RAID, Fibre Channel and al. -- -------------------------------------------------- Emmanuel Florac www.intellique.com -------------------------------------------------- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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