To ZIL or not to ZIL; that is indeed the question. (FreeNAS n00b needs help)

Discussion in 'FreeBSD and FreeNAS' started by michaeld, Mar 11, 2013.

  1. michaeld

    michaeld New Member

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    This is my first foray into running a non-Windows OS for my storage. TBH, I need a GUI, so FreeNAS immediately appealed to me. I've set it up with just two spinners in a mirror and have been testing it out for a few days now and it's been great. Stable and easy to use. Later this week when my M1015 arrives and I flash it to LSI9211-IT mode I will put move my NAS data to it (after a rebuild).

    For all intents and purposes, my home NAS data is relatively static. My NAS doubles as a media server over a wired Gigabit network. HD video, photos, saving Office docs for work...you get the idea. According to the FreeNAS 8.3.0 User's Guide, based on my type of data I don't need a ZIL. But is there BENEFIT to having one anyway? Potential downside? Due to the fact that FreeNAS runs off a USB stick, I currently have a Samsung 830 SSD sitting gathering dust. As I understand it, there is always a ZIL; the OS just writes it to the system drive (USB stick).

    I've already told you the type of data. The hardware for the server is:

    Supermicro X9SCA-F
    16GB ECC RAM
    Xeon 1230V2
    IBM M1015 (flashed to 9211-IT)
    Six Samsung 500GB spinners (plan to make 2 separate RaidZ arrays and then pool them, if that's the correct terminology)
    OS running off 8GB USB stick
    Seasonic 850w PS
    4U rackmount case
    Awesome DVD burner with sticking drawer

    I know this system is total overkill for a home file server, but #1, I have the hardware and it's not doing anything else and #2, idle power usage for this system is less than half of my current Core 2 Quad/DDR2 based file server (CPU+PCI-E video card+non-80+ Bronze PS in other system).

    Thanks for educating me on ZILs.
     
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    Last edited: Mar 11, 2013
  2. Jeggs101

    Jeggs101 Well-Known Member

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    my suggestion:

    try without. if you need more performance; try with.
     
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  3. mobilenvidia

    mobilenvidia Moderator

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    ZIL is best placed on a RAM Disk ?
     
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  4. PigLover

    PigLover Moderator

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    The only benefit of Zil is an improvent in write-IOPs. There is no other benefit. For your use case (relatively static data, media server, etc) there is no need for increased write-IOPs.

    If there is no separate Zil then the log goes onto the pool itself, not onto the rpool. Having a Zil won't move any writes off of the boot USB.

    You can certainly find a better use for your 'spare' SSD.
     
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  5. Patrick

    Patrick Administrator
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    I think that is what I would suggest as well. The caveat is if one wanted to show off excess performance for some reason.
     
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  6. michaeld

    michaeld New Member

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    Thanks very much, everyone. I lurk quite a bit on this forum and knew you guys have lots of experience with Unix and Linux in various flavors and scenarios. I knew I'd get a solid, real-world answer. :) I just want to set this up correctly from the get-go and not have to worry about it for a good while. I'm really liking FreeNAS so far. It's Windows-like with the GUI, very granular, like the Windows Server OSes I'm used to, but without the price tag, like I'm also used to. LOL! Thanks again.
     
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  7. dswartz

    dswartz Active Member

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    Also a separate ZIL makes no sense on RAM disk, as it's supposed to be like a journal, and a crash will nuke it.
     
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  8. Biren78

    Biren78 Active Member

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    Very important comment. ZIL goes on a bullet proof ssd not RAM
     
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  9. Thatguy

    Thatguy New Member

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    I have a reasonable array at home. Recently put in some Intel 520's as both Cache and ZIL, and honestly 98% of the time they make no difference, and the other 2% it's debatable.

    If you have a write heavy array, or are doing a lot of synchronous writes (Such as vmware vms over NFS) then a ZIL is great. If you have a lot of users accessing the same content, Cache is more beneficial.

    Also, if all your disks are on the same controller, I'd just do one single raidz2, instead of two raidz's.

    Also, ramdisks to hold a ZIL is silly, as ZFS is great in terms of memory management.
     
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  10. dswartz

    dswartz Active Member

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    " Also, ramdisks to hold a ZIL is silly, as ZFS is great in terms of memory management. "

    Not sure what you mean here, but memory management has nothing to do with why putting your ZIL on a ramdisk is a terrible idea.
     
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  11. jtreble

    jtreble Member

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    You might also want to consider SSDs that have capacitors for your ZFS ZIL device (e.g., Intel 320-series ...).
     
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  12. mrkrad

    mrkrad Well-Known Member

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    Databases typically use drives for linear writes. TPCC will use SSD for database and 24 15k drives in raid-0 for redo - SSD may not be the fastest?

    Otherwise you'd need to buy some superspeed slc sand force drives to take the punishment of a journal drive. Those intel SLC drives 24gb seem if you had enough in raid-10 might be fast enough.
     
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