Using SSDs in a HDD pool for more storage

TrueNAS General
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1

Here is my current drive setup as you can see complete mirrors across the board.

disks
disks2110×895 67.5 KB

I’m in the process of case swapping & my new case will have less space for 2.5" drives.

So i have swapped out my all my spinning rust 1TB WD Red drives for WD RED SA500 drives (6 in total) now 2 are in their own pool (download) I assume i’me fine to enable auto trim on that just fine?

My main question is can i also do that for the main volume as that is a mix of HDD and SSD storage or do i have to setup a cron job from trim specfically for the ssd storage? (or have i been a moron completyely by mixing the storage types)

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Mixing storage types is unlikely to help you much re: pool performance as parity bits are stored all over the pool. Thus, the HDDs will hold you back.

If you have a excess of reliable SSDs and want to speed up some functions like directory browsing as well as small file performance, then have a look at my sVDEV resource. That may be an option though I wonder if a new pool would be advisable…

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My plan wasn’t to add any sort of l2arc I just wanted to add as much storage as possible to my main pool in the 2’5" form factor.

Like I said I’m just wondering about good practice when it comes to have that pool be mixed like it is in regards to using or not using trim. (The main pool is entirely media storage so once written it would be mostly reads from then on)

4

Then your way forward is “full SSD”, since 2.5" spinning drives over 2 TB are all SMR.

As for “good practice”, I’m afraid there’s no experience with such mixing of HDDs and SSDs for capacity and no recommendation from the community.

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I’m aware what i’ve done is very much an edge case but as they are just storage and not any sort of cache simply ensuring smart and peroidic specific trim on them should be fine right as they’re mirrored.

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I believe the OP is replacing HDs with SSDs? Right?

As long as the SSDs have sufficient endurance and can sustain the write load required, then it should be fine if a few disks in the pool are faster.

Doesn’t make sense to continue investing in small 2.5” HDs these days.

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This is correct I have, my question is simply how do I structure a cron job to trim specifically on those SSDs in the mixed pool. (or if it’s even required)

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I think you just turn auto-trim on on the pool.

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Are the HDDs ignored with auto-trim? :thinking: