Bob Friesenhahn <bfrie...@simple.dallas.tx.us> wrote: > Yes of course. Properly built SSDs include considerable extra space > to support wear leveling, and this same space may be used to store > erased blocks. A block which is "overwritten" can simply be written > to a block allocated from the extra free pool, and the existing block > can be re-assigned to the free pool and scheduled for erasure. This > is a fairly simple recirculating algorithm which just happens to > also assist with wear management.
I believe you make a mistake with this assumption. - The SSD cannot know which blocks are currently not in use. - In special with a COW filesystem, after some time all net space may have been written to but the SSD does not know whether it is still used or not. So you see s mainly empty filesystem while the SSD does not know this fact. - If wou write not too much to a SSD, it may be that the spare space for defect management is sufficient in order to have suficient prepared erased space. - Once you write more, I see no reason why a COW filesystem should be any better than a non-COW filesystem. Jörg -- EMail:jo...@schily.isdn.cs.tu-berlin.de (home) Jörg Schilling D-13353 Berlin j...@cs.tu-berlin.de (uni) joerg.schill...@fokus.fraunhofer.de (work) Blog: http://schily.blogspot.com/ URL: http://cdrecord.berlios.de/private/ ftp://ftp.berlios.de/pub/schily _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss