On 2 jan 2010, at 12.43, Joerg Schilling wrote: > Ragnar Sundblad <ra...@csc.kth.se> wrote: > >> I certainly agree, but there still isn't much they can do about >> the WORM-like properties of flash chips, were reading is pretty >> fast, writing is not to bad, but erasing is very slow and must be >> done in pretty large pages which also means that active data >> probably have to be copied around before an erase. > > WORM devices do not allow to write a block a secdond time.
(I know, that is why I wrote WORM-like.) > There is > a typical 5% reserve that would allow to reassign some blocks and to make it > appear they have been rewritten, but this is not what ZFS does. Well, zfs kind of does, but especially typical flash SSDs do it, they have a redirection layer so that any block can go anywhere, so they can use the flash media in a WORM like style with occasional bulk erases. > Well, you are > hoewever true that there is a slight relation as I did invent COW for a WORM > filesystem in 1989 ;-) Yes, there indeed are several similarities. /ragge _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
