On Tue, 21 Oct 2008, MC wrote: > > There is a fusion-io user here claiming that the performance drops > 90% after the device has written to capacity once. Does fusion-io
Isn't this what is expected from FLASH-based SSD devices? They have to erase before they can write. The vendor is kind enough to deliver a pre-erased drive so the user feels an initial rush of exhilaration and feels good about the purchase. With standard hard drive interfaces the drive does not know if written data is useful or not so it can only erase when an overwrite is requested. This is because with hard drives, there is no need to "free" any data on the media. Usually the SSD's erase block size is larger than the filesystem block size so more data needs to be erased than will be written, so some pre-existing data needs to be read and restored (potentially placing it at risk). With a higher level interface (e.g. to ZFS) then freed regions can be erased once they are added to the filesystem free list and will hopefully be erased by the time they are used again. It seems that optical media often support an erase mechansim so perhaps there is something in the IDE/ATA/SATA/SCSI/SAS protocols which can be used to explicitly erase blocks. Bob ====================================== Bob Friesenhahn [EMAIL PROTECTED], http://www.simplesystems.org/users/bfriesen/ GraphicsMagick Maintainer, http://www.GraphicsMagick.org/ _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
