SSD headroom

I’ve been checking out the possibility of using a couple of SSD’s for sample drives but I’ve seen some statements on the web about needing to leave 50% of head room in order to be hassle free using SSD’s; is this really true or is the normad HDD 20% enough for SSD also?


This is something which requires deeper knowledge about how SSDs really (!) work and about the difference between “reading” and “writing”.

Let me explain:

  1. This is not “head room”, this is about leaving space free to allow for fast writes
  2. This was far more important back in the day when SSDs didn’t have TRIM capability (and no garbage collection either)
  3. Be aware, though, that TRIM may not work when you use the SSDs in a RAID configuration
  4. Since your sample drives will most probably be 99% reads, there is no need to leave that insane amount of space free

Bottomline: it’s outdated “knowledge”. People still have lots of misconceptions about SSDs (similar to the misconceptions about SMT / Hyperthreading), because the early models HAD problems.

Today things are different.

@ Chris.

Tanx for that info.
Excellent explanation.

Do you know if the same info holds true for ‘Flash’ drives? (cell phones, pads etc)

Depends on the controllers used. I don’t think, though, that for usual applications (including mobile DAWing) this is of any concern.

A flash memory in it’s slowest state is still much faster than a hard disk, and for recording audio, hard disks were usually fast enough.

Read speeds are never affected by how much space is used on a flash memory device.

headroom is not the correct term imo. It looks like the OP is referring to the overprovisioning, and that is still very needed to take into account on SSD’s.

But: when you buy a formatted SSD, the overprovisioning will already be taken into account by the manufacturer, and your space where you can save to is a little smaller then the space the box indicates. (f.e. 256 Gig = 220 Gig harddisk)

And: You can tweak the overprovisioning using the included software of the SSD manufacurer. But best practice is to leave 7% of the max capacity at all times imo.

kind regards,

to add a litlle further on the topic:

I would take the intended usage into account when buying an ssd.
F.e. if the usage is solely for storing samplebanks, then i would opt for a cheap SSD (f.e. EVO-types). The number of W/R is lower for those SSD’s, but you probably will be writing very few times on such an SSD. Overprovisioning is also hardly needed for such drives and can be lowered to allmost 0.
F.e. if the usage is for an operating system, the W/R usage is much more intense, and there i would opt to use the standard overprovisioning delivered by the manufacturer and also opt for a better (and more expensive) SSD.

kind regards,

Well, what I really wanted to know was how full can I go with an SSD used for sample playback with a few writes and a lot of reads. If it was necessary to leave 50% blank then it was going to be more expensive to use SSD than I had hoped for. However, it seems that for sample drives 10% should be good enough, i.e., I can put 90% of capacity worth of samples on an SSD.

I think I will go for 2 256 SSD instead of one 512 SSD for streaming purposes.

Thank you very much,

I’d suggest getting 2 Samsung 850 Pro devices. :slight_smile:

For sample drives, there is no reason to leave ANY spare space.

The spare space was only to allow there to be a big enough pool of spare blocks so that write exhaustion (10,000 writes per block) did not occur during the likely life of the drive.

For hobbyist’s DAW use as a project drive, as I enumerated in this Re: Buying a new PC - advise please thread post, an SSD is likely to last about 100 years before ANY blocks become unwritable with only 15GB of spare space. For a professional studio, they should get over three years with only 100GB spare.

Those were likely worst case figures, but the drive would probably suffer a catastrophic electrical failure before write limits were reached.

Note that the non-loss lifetime is directly proportional to the space capacity for a given usage pattern, but you can put your own usage values into the formulae to derive how much spare capacity you need to leave on an SSD.