It's a good point, of course. Ideally we would be able to prioritize data and place them on 15k versus 7.2krpm disks, etc. However you get to a point where's there's only incremental benefit. For that reason, the scope of this project was simply to take advantage of SSD and HDD in hybrid. Of course, you could register the same complaint about the ZFS SSD caching: why not take advantage of faster vs. slower spinning disks? Unfortunately it just wasn't in the scope of our 12-week project here. That's not to say it *shouldn't* be done in the future, of course! And, incidentally, you could hack it together at this point by setting the /sys/block/<blockdev>/queue/rotational flag to 0 and using it like an SSD. :) BC On Fri, Aug 13, 2010 at 8:14 AM, Andrey Panin <pazke@xxxxxxxxxxxxxx> wrote: > On 224, 08 12, 2010 at 05:29:37PM -0500, bchociej@xxxxxxxxx wrote: >> From: Ben Chociej <bchociej@xxxxxxxxx> >> >> Modified mkfs.btrfs to add hot data relocation option (-h) which >> preallocates BTRFS_BLOCK_GROUP_DATA_SSD and >> BTRFS_BLOCK_GROUP_METADATA_SSD at mkfs time for future use by hot data >> relocation code. Also added a userspace function to detect whether a >> block device is an SSD by reading the sysfs block queue rotational flag. > > IMHO this policy is too inflexible. What if I have large array of slow SATA > disks and some fast SAS ones ? > -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
