Question for the TrueNAS experts - BLUF I am concerned about the resilvering speed of a replacement drive while in the middle of attempting to upgrade one of my vdevs (from 6tb drives to 18tb drive). I have a 12 bay Supermicro server that has 3x vdevs with 4x drives in each in a raiz1 (one spare pe…

I don’t know if this is your issue but SDJ is a Barracuda and that is probably a SMR type drive and may be causing issues. SMR vs CMR ServeTheHome [image] WD Red SMR vs CMR Tested Avoid Red SMR We tested WD Red SMR v CMR drives to see if there was indeed a significant impact with the ch…

@NugentS Sure thing. The table of the current drives is below. XXX was removed and replaced with what is currently in sdj, YYY is a spare. NAME MODEL SIZE ROTA TYPE TRAN SERIAL VENDOR Manufacturer Human‑Readable Model Name sdb TOSHIBA HDWG51JUZSVA 16.4T 1 disk sas 2590A00KFWQH ATA Toshiba …

@SmallBarky - yes sir, that certainly looks like it could be the problem. I verified that the drive is SMR. That Seagate drive is on the way back to Amazon to be replaced with Toshiba N300 8TB NAS 3.5-Inch Internal Hard Drive - CMR SATA 6 GB/s 7200 RPM 512 MB Cache - HDWG780XZSTA. I will post bac…

I just checked another 6TB drive I had attempted to resilver to and was equally as slow - WD60EZAZ - confirmed it is SMR as well. I think you figured out the problem, can’t believe I didn’t realize these drives were SMR and that it made such a huge difference during resilver. I will know for sure …

I suspected SMR when you mentioned very slow resilver. :slight_smile:

BTW, I did extensive searching with paid accounts set for the highest level of research mode on Grok, Copilot and ChatGPT to search for possible causes of slow resilver and never a single mention of SMR at all. I specified excluding hardware failures, maybe that screwed it up. You’d think at this …

You trust a dumb pattern matching program? Mind you I am fairly suprised it didn’t bring anything up - its a fairly well known issue in the technical press. I did a google for “ZFS Slow Resilver” and there is nothing obvious in the first page of results that mention SMR - you have to follow up on …

No, haha, I don’t trust them at all, but I do know they can run 5000 search queries faster than I can manually. I’ve found them to be reasonably useful for similar search type activities - and it did generate the table of hard drives with the human readable make/model column. I don’t pay for them,…

Very slow resilvering speed

TrueNAS General

winnielinnie September 4, 2025, 12:15am 11

Don’t forget to enable “ghost compression” with zfs set compression=ghost.

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Very slow resilvering speed

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