Daniel J Blueman wrote: > On Fri, Jan 23, 2009 at 1:56 PM, Colin Watson <[email protected]> wrote: >> On Fri, Jan 23, 2009 at 12:04:33AM +0000, Daniel J Blueman wrote: >>> In order to maximise user experience thus performance, we need to >>> ensure the disk partitions created on SSDs/USB flash drives/RAID >>> arrays are 4KB (perhaps up to 128KB) aligned. There are considerable >>> benefits with the flash/RAID controller opening half as many >>> pages/stripes on small reads. This pays better with slower SSDs in eg >>> netbooks. >>> >>> Patches have entered the upstream kernel to detect when drives are >>> solid-state [1], though the dust hasn't settled on the interface. >>> >>> How acceptable would getting the userspace partitioner changes into >>> Jaunty if proven to be stable and robust? >> >> This seems like something that could be added as a libparted constraint >> without *too* much pain. If and only if the corresponding kernel changes >> go into the Ubuntu kernel (work with [email protected], I >> think), I agree that we should change the partitioner too, and pass the >> changes to parted upstream, although I would add that the changes need >> to be reasonably simple and elegant as well as stable and robust; I only >> like partitioner code that I can understand. :-)
...and accompanied by thorough tests. > I've checked into this, and since libparted sees the SATA block device > as SCSI, it doesn't perform the expected ATA 'identify' command to > fill out the 512 bytes of device info, of which (short) word 217 is > device RPM, defined to be 1 on newer compliant SSDs. The kernel uses > this word to detect if a device is an SSD or not, so I suggest we use > the same. > > Anyone think of objections to calling the ATA identify ioctl to fill > out the structure, then storing this flat for later use in constraint > checking? If the SCSI device supports it also, fine, else nothing > lost. > > For now, a 1MB starting offset for an SSD seems safest, and is what MS > Windows 7 and Server 2008 use, thus a number of vendors will also be > testing/optimising with this case too. Does this really need to be SSD-specific? I hear that this (alignment) is high priority also for many of the big new disks, since they have 4k-byte sectors. Without better alignment, their performance will suffer, too. _______________________________________________ parted-devel mailing list [email protected] http://lists.alioth.debian.org/mailman/listinfo/parted-devel
