On Monday February 18, keld@xxxxxxxx wrote: > On Mon, Feb 18, 2008 at 03:07:44PM +1100, Neil Brown wrote: > > On Sunday February 17, keld@xxxxxxxx wrote: > > > Hi > > > > > > > > It seems like a good way to avoid the performance problems of raid-5 > > > /raid-6 > > > > I think there are better ways. > > Interesting! What do you have in mind? A "Log Structured Filesystem" always does large contiguous writes. Aligning these to the raid5 stripes wouldn't be too hard and then you would never have to do any pre-reading. > > and what are the problems with zfs? Recovery after a failed drive would not be an easy operation, and I cannot imagine it being even close to the raw speed of the device. > > > > > > > But does it stripe? One could think that rewriting stripes > > > other places would damage the striping effects. > > > > I'm not sure what you mean exactly. But I suspect your concerns here > > are unjustified. > > More precisely. I understand that zfs always write the data anew. > That would mean at other blocks on the partitions, for the logical blocks > of the file in question. So the blocks on the partitions will not be > adjacant. And striping will not be possible, generally. The important part of striping is that a write is spread out over multiple devices, isn't it. If ZFS can choose where to put each block that it writes, it can easily choose to write a series of blocks to a collection of different devices, thus getting the major benefit of striping. NeilBrown - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
