Experience of QLC drives - Be aware

[sityeuropa]

I've started to swap out my Crucial P3 drives as the performance when you have filled them a little is very bad.
The more storage that is used on them thhe more this will diminish the write speeds. I don't know the exact numbers but when copying big files you will constantly hit bottlenecks.

After 250GB the transfer will drop to around 80MB sec

They are worse than a Crucial MX500 for copying large files.

 

[Armageus]

The issue is they use a portion of the available space as a cache operating in a faster mode (e.g. like earlier SLC or MLC based nand).

If either there is no capacity available to operate in this mode (because the drive is nearly full) then you will get slowdown.

Equally because this cache is only a limited amount, if you transfer significant amounts of data then this cache gets filled and is unable to recover leading to slower speeds.

Edit:
It's not unexpected behaviour and has been well documented

Crucial P3 SSD Review: Solid Secondary SSD

The P3 is an efficient budget drive with capacity to spare

www.tomshardware.com

 

[sityeuropa]

I knew about the Cache but just just wasn't expecting the drops to be as low as 100 MB for single file transfers.
Probably did just assume with how old the MX500 SSD was and the jumps advertising GB/sec write speeds. Surely it wouldn't be as worse in that area than it.

Didn't know MX500 is TLC so I suppose it makes sense as they are still around £220 for 4tb.

 

[Tetras]

I knew about the Cache but just just wasn't expecting the drops to be as low as 100 MB for single file transfers.
Probably did just assume with how old the MX500 SSD was and the jumps advertising GB/sec write speeds. Surely it wouldn't be as worse in that area than it.

Unfortunately the cache on both QLC & TLC drives tends to hide how slow they really are, you definitely have to buy QLC carefully if you're doing very large file transfers.

Didn't know MX500 is TLC so I suppose it makes sense as they are still around £220 for 4tb.

The endurance on these drives is pretty low, the 2TB is 700 TBW and the 4TB is 1000 TBW, whereas Kingston's KC600 which uses similar hardware, but guaranteed TLC has 1200 TBW in the 2TB capacity and WD's Red SA500 has 2500 TBW in the 4TB capacity.

There have been rumours for awhile that Crucial use QLC in the MX500, at both 2TB and 4TB capacity and the low endurance and lack of specification (about which type of NAND they use) would support that theory. Though, admittedly the endurance on the P3 is significantly worse than the MX500, at just 440 TBW in 2TB capacity.

 

[Cyber-Mav]

Qlc drive is fine for game use. Write once and then mostly read