iPhone 12 Pro Max I have about 9GB storage left out of 128 GB and my iPhone 12 Pro Max becomes laggy when multiple apps are open in the background

[jordysak]

I have about 9 GB storage left out of 128 GB and my iPhone 12 Pro Max becomes laggy when multiple apps are open in the background

- ‘background app refresh’ off

As soon as I free more space everything works as normal, but like now where I have about 9GB left of storage switching between apps is very hard as there are lags and the device is struggling to keep many apps open. This is all solved when I free up more storage. I know this is due to the fact that when you open apps in background they need to store temporary cache files hence why free storage is needed (correct me if I’m wrong) ..but I’m just wondering, isn’t 9 GB still a lot of storage? Isn’t requiring more of 9GB of free space a bit too much to keep the device working normally?

 

[Apple_Robert]

You need to free up some space ASAP. With SSD, you need to keep at least 20% free of total usable space for optimal performance.

 

[Htsi]

Doesng matter on my iPad. Reset and restore and keep background refresh on. Either way advise above is also factual.

 

[jordysak]

You need to free up some space ASAP. With SSD, you need to keep at least 20% free of total usable space for optimal performance.

Wow, that’s amazing to know! Is this facts? Not doubting your knowledge, just trying to understand this; so essentially, if a device has 128GB of storage I have to have 25.6 GB free for it to not lag.. whereas if the device has 64GB of storage I have to have 12.8 GB of free storage , correct?

 

[jordysak]

Doesng matter on my iPad. Reset and restore and keep background refresh on. Either way advise above is also factual.

With background refresh on it would be correct to assume that everything works smoothly in the background but it comes to the fact that it consumes a lot of battery.
Does yours work fine with background activity off and less than 20% of tot storage available?

 

[Htsi]

With background refresh on it would be correct to assume that everything works smoothly in the background but it comes to the fact that it consumes a lot of battery.
Does yours work fine with background activity off and less than 20% of tot storage available?

I do not keep refresh off. Have had 256 ipad show 2gb free and still no lags.

 

[Apple_Robert]

Wow, that’s amazing to know! Is this facts? Not doubting your knowledge, just trying to understand this; so essentially, if a device has 128GB of storage I have to have 25.6 GB free for it to not lag.. whereas if the device has 64GB of storage I have to have 12.8 GB of free storage , correct?

Yes, for optimal performance for SSD and the device. The same holds true for Macs and iPads.

 

[jordysak]

I do not keep refresh off. Have had 256 ipad show 2gb free and still no lags.

Yes if your background refresh is on then this is the way it should work, but my original query was in case of background refresh off

 

[JohnnyGo]

Gotta keep most media files (video, photos) in cloud storage.

Be diligent with your messaging apps (iMessage, WhatsApp) as they also accumulate a lot of media files).

Next time go for 256Gb storage.

 

[Ledsteplin]

With background refresh on it would be correct to assume that everything works smoothly in the background but it comes to the fact that it consumes a lot of battery.
Does yours work fine with background activity off and less than 20% of tot storage available?

Background App Refresh doesn't use that much battery. It helps apps run more efficiently in the background, saving resources. Apple wouldn't have implemented it, if it used up the battery. I've tried it with all apps on, and all off. Don't notice any difference.

 

[rui no onna]

Wow, that’s amazing to know! Is this facts? Not doubting your knowledge, just trying to understand this; so essentially, if a device has 128GB of storage I have to have 25.6 GB free for it to not lag.. whereas if the device has 64GB of storage I have to have 12.8 GB of free storage , correct?

There are plenty of tests on the effect of overprovisioning on SSD performance and longevity. That said, iPad performance is a combination of a variety of different things. For you, it seems your usage/workload has hit a storage bottleneck.

 

[jordysak]

Background App Refresh doesn't use that much battery. It helps apps run more efficiently in the background, saving resources. Apple wouldn't have implemented it, if it used up the battery. I've tried it with all apps on, and all off. Don't notice any difference.

Sorry , do you mean to say that you have tried turning off background app refresh for all apps and on without noticing any effect? May I ask what’s your free storage at the moment?

Gotta keep most media files (video, photos) in cloud storage.

Be diligent with your messaging apps (iMessage, WhatsApp) as they also accumulate a lot of media files).

Next time go for 256Gb storage.

On that note, do you perhaps know a way of storing selective photos to iCloud and keep others locally?

 

[jordysak]

There are plenty of tests on the effect of overprovisioning on SSD performance and longevity. That said, iPad performance is a combination of a variety of different things. For you, it seems your usage/workload has hit a storage bottleneck.

Thank you for the detailed information. I was in fact trying to understand if this is normal behaviour, but after reading your reply seems like it is.
I’ll wait for others with less than 20% storage available on their device to see if this happens with everyone , but your explanation definitely helped and I definitely learnt something new

 

[Apple_Robert]

Thank you for the detailed information. I was in fact trying to understand if this is normal behaviour, but after reading your reply seems like it is.
I’ll wait for others with less than 20% storage available on their device to see if this happens with everyone , but your explanation definitely helped and I definitely learnt something new

The behavior you have seen is not isolated and will happen to every device with a SSD and low storage. No need to take a poll. Free up some space. Facts have been presented, not opinions. You can search for yourself if you need more prompting.

 

[JagRunner]

Dang, should have went with the 256 storage.

 

[HDFan]

Yes, for optimal performance for SSD and the device. The same holds true for Macs and iPads.

This is a generic rule for random access storage media, such as disks, SSDs, etc., pretty much regardless of device - desktop, tablet, phone, etc. The actual number is device specific. Some NAS units have software that calculates the best number for you. The last time I ran the tool for a NAS SSD the number was 30%.

What is unclear to me is if this number changes when you get very large disks/arrays. For example if you have a 128 TB RAID 5 device, 20% free would be 25 TB. Seems to me a few TB would be enough?

 

[rui no onna]

This is a generic rule for random access storage media, such as disks, SSDs, etc., pretty much regardless of device - desktop, tablet, phone, etc. The actual number is device specific. Some NAS units have software that calculates the best number for you. The last time I ran the tool for a NAS SSD the number was 30%.

It's really mostly based on workload and data sets. Mind, some enterprise SSDs have very high built-in OP to begin with for durability or have tunable OP.

SSD Over-Provisioning And Its Benefits | Seagate US

https://media-www.micron.com/-/media/client/global/documents/products/technical-marketing-brief/ssd_flex_capacity_feature_tech_brief.pdf

What is unclear to me is if this number changes when you get very large disks/arrays. For example if you have a 128 TB RAID 5 device, 20% free would be 25 TB. Seems to me a few TB would be enough?

It's per drive so no, doesn't really change. As mentioned, whether it should be 20% or something else depends on workload. That said, I think on most SSDs, going from default 7% OP (GB/GiB disparity) to ~20% greatly improves performance consistency and minimum performance level.

I haven't seen OP effects on recent AnandTech reviews but here's a comparison from an older review.

default OP

with 25% OP

 

[rui no onna]

Found AnandTech's deep dive article.

Exploring the Relationship Between Spare Area and Performance Consistency in Modern SSDs

www.anandtech.com

The above article was written by Anand Lal Shimpi who is now part of Apple's hardware division.

Charts are logarithmic so the performance differences are bigger than the images suggest.

 

[HDFan]

It's per drive so no, doesn't really change.

The 15% recommendation for Windows in the past was due to the fact that defragmentation would not run <15% disk free.

This off-topic, but sort of related.

I found a couple of references (for NAS units) which indicated you could go to 0%, depending upon how the device was being used. Assume the file system may be a factor here.

https://www.reddit.com/r/techsupport/comments/3497pa
https://www.reddit.com/r/synology/comments/ivxg9c
To make it confusing I checked with Promise support and their recommendation for their hardware RAID 5 units is 20%:

"for example, if you getting read/write speed around 1100MB/sec [with 0% usage], at 80% you will get 900+ read/write speed"

which I suppose is a generic answer not limited to those using Promise hardware, I/O drops as usage increases.

 

[rui no onna]

The 15% recommendation for Windows in the past was due to the fact that defragmentation would not run <15% disk free.

This off-topic, but sort of related.

I found a couple of references (for NAS units) which indicated you could go to 0%, depending upon how the device was being used. Assume the file system may be a factor here.

https://www.reddit.com/r/techsupport/comments/3497pa
https://www.reddit.com/r/synology/comments/ivxg9c
To make it confusing I checked with Promise support and their recommendation for their hardware RAID 5 units is 20%:

"for example, if you getting read/write speed around 1100MB/sec [with 0% usage], at 80% you will get 900+ read/write speed"

which I suppose is a generic answer not limited to those using Promise hardware, I/O drops as usage increases.

And this is where workload and data sets factor in. If you're just using the NAS to store movies, music, etc., you really only need to upgrade storage when you need more space and there's no noticeable penalty to filling to capacity. Chances are you'll be bottlenecked by network speeds anyway.

Regarding the answer by Promise support, is that in reference to SSDs or HDDs?

Due to geometry, HDDs have fast and slow portions depending on physical location.

In the XP+HDD days, I short-stroked my drives to keep OS in the high performance area (750GB-1TB at the time). I'd install the OS and programs on a 100-200GB partition which always has plenty of free space while the remainder of the drive is formatted as one giant partition to hold static data (typically media files). Pagefile goes into a secondary drive on a 100GB partition while the remainder is again formatted as one giant partition. I can fill the secondary partitions full of videos without OS and programs performance being affected.

On SSDs, the physical location of the data doesn't really matter. However, I believe most modern SSDs make use of both a fixed SLC cache + free space as dynamic SLC cache. As the SSD gets full, the smaller the cache becomes reducing peak performance with sustained writes.

The question is what is your usage pattern and how big is the data set you normally write? If you only write around 20GB regularly, 20% or 400GB OP on a 2TB SSD is obviously overkill.

In the case of the OP, 9GB free out of 128GB is likely triggering some read-erase-program scenario. I do wonder if TRIM works on iOS and how aggressive garbage collection is on Apple's SSD controller.

 

[The Game 161]

don't you use iCloud?

 

[Ledsteplin]

Sorry , do you mean to say that you have tried turning off background app refresh for all apps and on without noticing any effect? May I ask what’s your free storage at the moment?

On that note, do you perhaps know a way of storing selective photos to iCloud and keep others locally?

Yes, tried it both ways, and notice no difference. I keep all my apps turned on for Background App Refresh.
For storage, I don't keep many songs downloaded local. They take a lot of space. No movies downloaded. Not many videos on my camera roll. I usually try to keep photos at a minimum. I upload most to Box and Dropbox. Right now it's mostly wallpapers. I keep messages in iMessage deleted. I delete notes I don't need in the Notes app. I keep photos in the Recently Deleted folder deleted. I don't use iCloud for photos. You can reduce the size of photos in settings, if you use iCloud.

iPhone 12 Pro Max

 

[Aceroller]

I don’t know all the tech behind it, but I have had many iPhones that only have a few GB of free storage left and they NEVER slowed down or lagged as the OP is describing.

 

[macdogpro]

My old iPhone 6 with 16gb storage sometimes only has 600-800 mb free space. No lags.

I do read about people recommending to leave 20-25% free space on SSD, but as far as I know it’s to preserve the longevity of the hardware, and never read something similar for a flash memory like on smartphones. Are those two things the same type of storage?

 

[cambookpro]

@jordysak , does the issue you’re describing match what people are experiencing in this thread?: https://forums.macrumors.com/threads/12-pro-stutter-when-closing-apps.2263484/

I think all the talk about storage and optimum free space etc is a red herring. This seems to be affecting a small proportion of users and isn’t correlated with storage use.