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Date: Sat, 01 Mar 2008 15:04:29 -0500 From: Bill Davidsen <davidsen@....com> To: Andreas Dilger <adilger@....COM> CC: Tomasz Chmielewski <mangoo@...g.org>, Theodore Tso <tytso@....edu>, Andi Kleen <andi@...stfloor.org>, LKML <linux-fsdevel@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>, linux-raid@...r.kernel.org Subject: Re: very poor ext3 write performance on big filesystems? Andreas Dilger wrote: > I'm CCing the linux-raid mailing list, since I suspect they will be > interested in this result. > > I would suspect that the "journal guided RAID recovery" mechanism > developed by U.Wisconsin may significantly benefit this workload > because the filesystem journal is already recording all of these > block numbers and the MD bitmap mechanism is pure overhead. > Thanks for sharing these numbers. I think use of a bitmap is one of those things which people have to configure to match their use, certainly using a larger bitmap seems to reduce the delays, using an external bitmap certainly help, especially on an SSD. But on a large array, without a bitmap, performance can be compromised for hours during recovery, so the administrator must decide if normal case performance is more important than worst case performance. -- Bill Davidsen <davidsen@....com> "Woe unto the statesman who makes war without a reason that will still be valid when the war is over..." Otto von Bismark -- 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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