On Tue, 27 Nov 2007, ChristopherD wrote:
At this point, I'm all ears...I don't even know where to start. Is ext2 not a good format for volumes of this size? Then how to explain the block device xfer rate being so bad, too? Is it that I have one drive in the array that's a different brand? Or that it has a different cache size?
Well, I have seen 3ware hwraid volumes slow down to 10 megabyte/s when writing, so I guess you're seeing a similar problem. It's due to the way raid5 works (needing to read before writing parity) and small caches.
If you need to write quickly, you should look into using software raid instead, then the raid5 sw raid subsystem has access to the entire ram block cache and hopefully don't need to read as much from the drives.
I don't know why you're only getting 4 MB/s, if you would have said 10-15 MB/s I wouldn't have been surprised at all, but 4 does seem to be on the low side. When I tried with 3ware, the type of filesystem chosen made very small difference.
-- Mikael Abrahamsson email: swmike@xxxxxxxxx - 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
