Which pool would a slog device benefit most?

Discussion in 'Proxmox VE: Installation and configuration' started by gregg098, Jun 15, 2019.

  1. gregg098

    gregg098 New Member

    Joined:
    Apr 5, 2018
    Messages:
    26
    Likes Received:
    2
    I have a Dell T30 with two ZFS pools. The first is a mirrored pool (rpool) of two S3700's created on install. This has the host OS and also my VMs/containers.

    The other pool consists of four 8TB hard drives setup basically as RAID10 in mirrored pairs.

    For KVMs, I run Windows 10 and Debian 9. Debian runs Docker with a bunch of Usenet stuff, UNMS, my test lab for Home Automation (use a dedicated NUC for the actual home automation setup), etc. I also play around with different Linux builds (Mint, Ubuntu, etc.) periodically. For containers, I have one for Plex and another that is just a file server. Nothing crazy for work load. Plenty of RAM as well.

    On the hard drives, I just store bulk files. Mainly my media for Plex and backups from other computers.

    I managed to snag a 16GB Optane NVMe module and a PCI to NVMe adapter for really cheap. I understand I don't really need it, but I got a good deal on it. If I install this, which pool would benefit the most with a SLOG device?

    The main pool, rpool, has pretty fast drives already. Pveperf shows about 4000+ fsyncs/sec
    The hard drive pool is obviously slower and shows about 300 fsyncs/sec

    I don't really do a lot of synchronous writes (the fact that my hard drives are an NFS destination for a few machines as a backup is probably it), but would like to utilize the Optane module. Which pool would show more benefit?
     
  2. sb-jw

    sb-jw Active Member

    Joined:
    Jan 23, 2018
    Messages:
    547
    Likes Received:
    47
    If you have constant (sequentia) Streams of big data (eg an ISO File) normally a Cache wouldn't help you here. If you have more smaller files and a bit more random (eg you work with Photoshop directly on the device) then a cache would help you.

    Keep in mind, you can destroy any cache device very fast with sequential streams.
     
  3. gregg098

    gregg098 New Member

    Joined:
    Apr 5, 2018
    Messages:
    26
    Likes Received:
    2
    Thanks for the reply. I'm not adding a cache device though, just a small SLOG. I don't think L2ARC would benefit me at all, less than adding a SLOG. As for wear out, Optane should hold out well in the long term (in my usage anyways).

    I did add it in last night and have tested it with both pools. I get roughly 10,000 fsyncs/sec with pveperf on either pool. These aren't real world test though. Reading into it more, I think it would be beneficial to stay on the hard drive datapool since I server files over NFS from there. Also, the rpool consists of Intel S3700's which are pretty fast as is.

    Open to any thoughts from anyone on this though.
     
  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.
    Dismiss Notice