FYI - virtually all non-super-low-end SSDs are already significantly over-provisioned, for GC and scratch use inside the controller.
In fact, the only difference between the OCZ "extended" models and the non-extended models (e.g. Vertex 2 50G (OCZSSD2-2VTX50G) and Vertex 2 Extended 60G (OCZSSD2-2VTXE60G)) is the amount of extra flash dedicated to scratch. Both the aforementioned drives have 64G of flash chips - it's just that the 50G one uses significantly more for scratch, and thus, will perform better under heavy use. Over-provisioning at the filesystem level is unlikely to significantly improve things, as the SSD controller generally only uses what it considered "scratch" as such - that is, while not using 10G at the filesystem level might seem useful, overall, my understanding of SSD's controller usage patterns is that this generally isn't that much of a performance gain. E.g. you'd be better off buying the 50G Vertex 2 and fully using it than the 60G model and only using 50G on it. -Erik On Tue, 2011-07-12 at 10:10 -0700, Henry Lau wrote: > It is hard to say, 90% or 80%. SSD has already reserved overprovisioning > places > for garbage collection and wear leveling. The OS level only knows file LBA, > not > the physical LBA mapping to flash pages/block. Uberblock updates and COW from > ZFS will use a new page/block each time. A TRIM command from ZFS level should > be > a better solution but RAID is still a problem for TRIM at the OS level. > > Henry > > > > ----- Original Message ---- > From: Jim Klimov <jimkli...@cos.ru> > Cc: ZFS Discussions <zfs-discuss@opensolaris.org> > Sent: Tue, July 12, 2011 4:18:28 AM > Subject: Re: [zfs-discuss] Pure SSD Pool > > 2011-07-12 9:06, Brandon High пишет: > > On Mon, Jul 11, 2011 at 7:03 AM, Eric Sproul<espr...@omniti.com> wrote: > >> Interesting-- what is the suspected impact of not having TRIM support? > > There shouldn't be much, since zfs isn't changing data in place. Any > > drive with reasonable garbage collection (which is pretty much > > everything these days) should be fine until the volume gets very full. > > I wonder if in this case it would be beneficial to slice i.e. 90% > of an SSD for use in ZFS pool(s) and leave the rest of the > disk unassigned to any partition or slice? This would reserve > some sectors as never-written-to-by-OS. Would this ease the > life for SSD devices without TRIM between them ans the OS? > > Curious, > //Jim > > _______________________________________________ > zfs-discuss mailing list > zfs-discuss@opensolaris.org > http://mail.opensolaris.org/mailman/listinfo/zfs-discuss > > _______________________________________________ > zfs-discuss mailing list > zfs-discuss@opensolaris.org > http://mail.opensolaris.org/mailman/listinfo/zfs-discuss -- Erik Trimble Java Platform Group - Infrastructure Mailstop: usca22-317 Phone: x67195 Santa Clara, CA Timezone: US/Pacific (UTC-0800) _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
