There had been a discussion of the topic on this list bout a onth ago, and I'd been told that similar ideas (compressed metadata/data in ARC/L2ARC) is on zfs dev agenda.
Regards, Andrey On Sun, Mar 28, 2010 at 2:42 AM, Stuart Anderson <ander...@ligo.caltech.edu> wrote: > > On Oct 2, 2009, at 11:54 AM, Robert Milkowski wrote: > >> Stuart Anderson wrote: >>> >>> On Oct 2, 2009, at 5:05 AM, Robert Milkowski wrote: >>> >>>> Stuart Anderson wrote: >>>>> I am wondering if the following idea makes any sense as a way to get ZFS >>>>> to cache compressed data in DRAM? >>>>> >>>>> In particular, given a 2-way zvol mirror of highly compressible data on >>>>> persistent storage devices, what would go wrong if I dynamically added a >>>>> ramdisk as a 3rd mirror device at boot time? >>>>> >>>>> Would ZFS route most (or all) of the reads to the lower latency DRAM >>>>> device? >>>>> >>>>> In the case of an un-clean shutdown where there was no opportunity to >>>>> actively remove the ramdisk from the pool before shutdown would there be >>>>> any problem at boot time when the ramdisk is still registered but >>>>> unavailable? >>>>> >>>>> Note, this Gedanken experiment is for highly compressible (~9x) metadata >>>>> for a non-ZFS filesystem. >>>>> >>>> You would only get about 33% of IO's served from ram-disk. >>> >>> With SVM you are allowed to specify a read policy on sub-mirrors for just >>> this reason, e.g., >>> http://wikis.sun.com/display/BigAdmin/Using+a+SVM+submirror+on+a+ramdisk+to+increase+read+performance >>> >>> Is there no equivalent in ZFS? >>> >> >> Nope, at least not right now. > > Curious if anyone knows of any other ideas/plans for ZFS caching compressed > data internally? or externally via a ramdisk mirror device that handles > most/all read requests? > > Thanks. > > -- > Stuart Anderson ander...@ligo.caltech.edu > http://www.ligo.caltech.edu/~anderson > > > > _______________________________________________ > 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
