Messages in this thread |  | | Date | Tue, 25 Sep 2001 09:06:02 -0400 | From | Chris Mason <> | Subject | Re: [reiserfs-list] Re: [PATCH] 2.4.10 improved reiserfs a lot, but could still be better |
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On Tuesday, September 25, 2001 02:54:58 PM +0200 Jorge Nerín <jnerin@juridicas.com> wrote: >> > Who says test.zero is a linear file and it's not scattered around the > whole disk and the fs layer is filling holes...? If it's the case the > write cache is a BIG win, just think that the fs writes a chunk at the > beggining of the disk, then another chunk at the end, then another near > the beginning, then... you get the picture, in this case the disk > reorders the seeks to best fit. > > If you want to try a REAL linear write do a dd if=/dev/zero of=/dev/hde7 > or whatever unused partition you have. >
Exactly, especially since during the dd you're going to seek back to the log for a few commit writes.
>From a filesystem point of view, I've spent hours and hours getting reiserfs to order the writes correctly to keep data consistent after a crash. Turning on writeback caching without a battery backup more or less throws all that work out the window. Don't do it.
For some people, a UPS counts as a battery backup, but there are lots of reasons that doesn't fly in any kind of production environment. If your job somehow depends on the data being safe, just get a raid controller with batter backed cache.
-chris
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