On Saturday 14 February 2009, Chris Mason wrote: > On Fri, 2009-02-13 at 23:31 +1100, Chris Samuel wrote: [Bonnie++] > > This is on a Dell E4200 with Core 2 Duo U9300 (1.2GHz), 2GB RAM > > and a Samsung SSD (128GB Thin uSATA SSD). > > Thanks for posting these, it is especially good to see the metadata ops > are still fast on this ssd. Not a problem - sorry for the delay in responding.. :-( > So, btrfs is doing ~28MB/s writes while writing the data twice and XFS > is doing 62MB writing it once. That's not too bad really. Yup, I'm very happy! > But, one important thing about the ssds is they stripe internally across > a bunch of flash storage, and then they have the FTL managing all the > writes. Ah... > So, if you make two partitions on a single device, a raid1 data write > from btrfs is very likely to result in two large IOs, which the FTL very > well might put directly adjacent to each other on the SSD. ...yes, I can see that could well happen. Bugger.. :-( > Duplicating the data does make it more likely you'll recover something > if the device goes bad, but two devices are still safer than one. Yeah, but pretty hard to do in a very light laptop! > I'm not saying the test isn't valid, I just want to make sure people > reading the list don't run off and partition their ssds in hopes of > getting raid ;) Agreed - I'm just hoping to be a bit safer than not having it.. ;-) cheers, Chris -- Chris Samuel : http://www.csamuel.org/ : Melbourne, VIC This email may come with a PGP signature as a file. Do not panic. For more info see: http://en.wikipedia.org/wiki/OpenPGP
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