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It is recommended that users maintain at least 25% free space on solid state drives for best performance - see http://www.howtogeek.com/165472/6-things-you-shouldnt-do-with-solid-state-drives/

For purposes of this question, let's assume the above is true.

Does this logic also apply to LVM2 logical volumes belonging to a volume group whose physical volumes are partitions on a solid state drive? In other words, for best performance, should we maintain 25% free space on each logical volume?

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  • 1. No, if the SSD itself has unallocated space, that's all that is required. 2. That "recommendation" is pretty much obsolete these days. Most modern SSDs already have spare unallocated space (e.g. that's why they have sizes like 120GB or 240GB rather than 128GB or 256GB) for wear-levelling, and write-endurances rivalling (or exceeding) that of HDDs.
    – cas
    Commented Jun 19, 2016 at 5:40

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It might make sense for special applications (disk sees lots of writes and is completely full) but you don't find those at home (and not on most servers, either).

In general SSD already have a built-in reserve, no need to worry about it yourself. Particularly if you intend to use any kind of TRIM/discard, anything that's trimmed is free too. Pointless to keep even more free space around (which is only free if it's never been written to or subsequently trimmed).

should we maintain 25% free space on each logical volume?

If you do this at all, don't do it "for each LV". This is about the whole disk, not about individual volumes.

That said, many filesystem start performing poorly and fragment heavily once they reach close to full state. ext* has a 5% root reserve by default to help avoid such situations from occuring. However that's another issue, not related to SSD in any way. And even so, 5% is too much (for a large filesystem). 25% definitely wayyy too much. Besides people naturally avoid 100% utilization of filesystems because "no space left on device" errors suck.

SSD is just another storage medium. You don't have to worry about write cycles.

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I do not see why the suggestion you link to wouldn't be applicable to you.

It merely explains that it's good to leave a sufficient amount of free space to prevent fragmentation. This recommendation can also apply to other types of drives but non sequential writes have a greater impact on SSD performance than hard drives (in terms of ratio between sequential and random).

There is yet another good reason to maintain more free space on SSD to compensate for certain sectors wearing out and relocating.

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