Performance-wise, I think you should go for mirrors/raid10, and separate the pools (i.e. rpool mirror on SSD and data mirror on HDDs). If you have 4 SSDs, you might mirror the other couple for zoneroots or some databases in datasets delegated into zones, for example. Don't use dedup. Carve out some space for L2ARC. As Ed noted, you might not want to dedicate much disk space due to remaining RAM pressure when using the cache; however, spreading the IO load between smaller cache partitions/slices on each SSD may help your IOPS on average. Maybe go for compression.
I really hope someone better versed in compression - like Saso - would chime in to say whether gzip-9 vs. lzjb (or lz4) sucks in terms of read-speeds from the pools. My HDD-based assumption is in general that the less data you read (or write) on platters - the better, and the spare CPU cycles can usually take the hit. I'd spread out the different data types (i.e. WORM programs, WORM-append logs and random-io other application data) into various datasets with different settings, backed by different storage - since you have the luxury. Many best practice documents (and original Sol10/SXCE/LiveUpgrade requirements) place the zoneroots on the same rpool so they can be upgraded seamlessly as part of the OS image. However you can also delegate ZFS datasets into zones and/or have lofs mounts from GZ to LZ (maybe needed for shared datasets like distros and homes - and faster/more robust than NFS from GZ to LZ). For OS images (zoneroots) I'd use gzip-9 or better (likely lz4 when it gets integrated), same for logfile datasets, and lzjb, zle or none for the random-io datasets. For structured things like databases I also research the block IO size and use that (at dataset creation time) to reduce extra work with ZFS COW during writes - at expense of more metadata. You'll likely benefit from having OS images on SSDs, logs on HDDs (including logs from the GZ and LZ OSes, to reduce needless writes on the SSDs), and databases on SSDs. Things "depend" for other data types, and in general would be helped by L2ARC on the SSDs. Also note that much of the default OS image is not really used (i.e. X11 on headless boxes), so you might want to do weird things with GZ or LZ rootfs data layouts - note that these might puzzle your beadm/liveupgrade software, so you'll have to do any upgrades with lots of manual labor :) On a somewhat orthogonal route, I'd start with setting up a generic "dummy" zone, perhaps with much "unneeded" software, and zfs-cloning that to spawn application zones. This way you only pay the footprint price once, at least until you have to upgrade the LZ OSes - in that case it might be cheaper (in terms of storage at least) to upgrade the dummy, clone it again, and port the LZ's customizations (installed software) by finding the differences between the old dummy and current zone state (zfs diff, rsync -cn, etc.) In such upgrades you're really well served by storing volatile data in separate datasets from the zone OS root - you just reattach these datasets to the upgraded OS image and go on serving. As a particular example of the thing often upgraded and taking considerable disk space per copy - I'd have the current JDK installed in GZ: either simply lofs-mounted from GZ to LZs, or in a separate dataset, cloned and delegated into LZs (if JDK customizations are further needed by some - but not all - local zones, i.e. timezone updates, trusted CA certs, etc.). HTH, //Jim Klimov _______________________________________________ zfs-discuss mailing list email@example.com http://mail.opensolaris.org/mailman/listinfo/zfs-discuss