On May 25, 2014, at 8:47 AM, Schweiss, Chip <c...@innovates.com> wrote: > Reservations don't keep ZFS from eventually writing to every assignable block > on the SSD. >
Disagree. SPA allocations are first fit and biased towards lower-numbered LBAs. This means that for the vast majority of cases, there is large unallocated space of significant magnitude. > This would work if Illumos did trim. Until then slicing and using less than > the entire capacity will keep the performance of the SSD high. > You are assuming that LBAs are exposed by SSDs. They are not. SSDs use their own COW file systems and the garbage collection will readjust the layout such that you can never be sure what pages are recycled or when. This is especially important for those cases that overwrite the same blocks many times, notably FAT and NTFS. > Also using a shift 12 or 13 helps by causing less write amplification. > Agree. Some SSDs, even expensive enterprise-grade SSDs, do a poor job of sub-4KB sector allocations. -- richard > -Chip > > On May 25, 2014 8:21 AM, "Richard Elling via illumos-discuss" > <discuss@lists.illumos.org> wrote: > > On May 24, 2014, at 3:32 PM, Günther Alka via illumos-discuss > <discuss@lists.illumos.org> wrote: > >> SSDs are the future of high performance storage. >> With most consumer SSDs overpovisioning is a common way to keep write >> performance high. >> >> On Linux you can use hdparm to create a host protected area with the main >> advantage that you do not need to struggle with partitions or slices - just >> use the whole disk as usual. >> >> read >> http://www.thomas-krenn.com/de/wiki/SSD_Over-Provisioning_mit_hdparm >> >> >> Has anyone compiled hdparm for Illumos or know about a Solaris tool to >> create a host protected area? > > But why bother overprovisioning with such a low-level tool? We use ZFS, if > you want to reserve some space, make a reservation :-) > >> >> sdparm? >> https://www.illumos.org/issues/2899 > > It should compile fine, OOB. > -- richard > > -- > > richard.ell...@richardelling.com > +1-760-896-4422 > > > > illumos-discuss | Archives | Modify Your Subscription -- richard.ell...@richardelling.com +1-760-896-4422 ------------------------------------------- illumos-discuss Archives: https://www.listbox.com/member/archive/182180/=now RSS Feed: https://www.listbox.com/member/archive/rss/182180/21175430-2e6923be Modify Your Subscription: https://www.listbox.com/member/?member_id=21175430&id_secret=21175430-6a77cda4 Powered by Listbox: http://www.listbox.com
