Extremely slow SD card

[Anamon2]

Hi all! I'm having some problems currently with my Z5 Compact and SD card storage.

I used to have a Sandisk Extreme 32GB microSDHC card in my Z5C without problem for more than half a year. About a month ago, I wanted to replace it with a Sandisk Ultra 64GB microSDXC, and I am having extreme issues with speed and battery consumption whenever I try to use it.

Some examples: when the camera app is set to store photos and videos on the SD card, just starting the camera app sometimes takes ages. Taking and saving pictures is slow. In some instances, the rotating saving animation will show for around 20 seconds, and in the end the photo is still not stored on the card, and lost. Spotify is unbearably slow when its storage location is set to SD card. There is a 5-10 second pause almost every time I switch to another track, during which the app will seem to freeze, there's no information about the currently playing title, etc. Scrolling through playlists often freezes too, with all tracks showing as "Unknown title - Unknown artist - Unknown album", until everything loads about 10 seconds later. I also get regular messages like "Track ont available", "Go online to open menu", or "Storage not found", which all go away after a couple of seconds and things work again. Both of these apps, camera and Spotify, work fine again as soon as I switch them back to internal storage. They both worked fine using the old SD card.

The phone has generally become very slow, in some cases it takes almost half a minute to even unlock. It has also strongly affected battery life. A full charge is now usually empty about 3-5 times faster than without the SD card inserted, probably because all the SD reading and writing takes so much longer than it should.

A benchmark shows a sustained write rate of around 12 MB/s for the card, which is still in specification for a class 10 card. But I don't think the sustained speed is the problem, it seems to be random file access. For exapmle, one of the measures I tried taking is clearing Spotify's cache, which had grown to about 10 GB in 3,000 files. Because the cache clearing in app settings seemed to freeze, I went to delete the folder in File Commander. There, it showed that deleting each single file took about 2-3 seconds until it would delete the next one. So deleting Facebook cache took more than 3 hours and almost emptied an entire battery charge. If I format the SD card, it seems quick for about half a day to a day, until performance and battery life crash again.

At this point I'm not sure what the problem is. I have a few possible theories:

• Might the specific SD card I have be defective, and could it work again if I just got it replaced?
• Is the difference between Ultra/Extreme the problem? They both have the same speed class, but Extreme are advertised as faster, and about twice as expensive. My other Sandisk card, which was an Extreme, worked well, but I'm not sure if it is because of that. File access time is not advertised as a distinguishing feature.
• Is the switch from 32 GB to 64 GB (and hence SDHC to SDXC) the issue? I.e., does the Z5C have any speed issues with SDXC cards, and should I just replace the card with an equivalent 32 GB model?
• Should I go with an equivalent card from a different manufacturer? Would it be possible that that solves the problem?

I was hoping that maybe someone here has some insight from their own experiences with SD cards used in phones of the Z5 lines, maybe had the same problem at some point and has any pointers on what the possible cause is.

Thanks!

Daniel

[Uliwooly]

@Anamon2

Which class is the new SD card?

[CameronT]

Hi @Anamon2,

There are three kinds of Speed Classes, "Speed Class", "UHS Speed Class" and "Video Speed Class."

As a characteristic of flash memory, actual transfer speed varies. Variable speeds are difficult to reliably record streaming content such as video because it requires a constant writing speed. Depending on the class of SD card you are using you can get anything from 2MB/s up to 90MB/s.

[Anamon2]

Thank you for your replies @uliwooly and @CameronT 

The old card was Speed Class 10, UHS Speed Class 3. The new card is Speed Class 10, UHS Speed Class 1. However, according to the specifications of the Z5 Compact, it only supports UHS Speed Class up to 1, so I'm not sure it should make a difference.

So the new card is, in fact, advertised as being slower, but I don't think that it should be nearly as slow as it is. As I mentioned, the phone is practically unusable with the card inserted. I used the same Class 10, UHS Class 1 cards in my DSLR, and only noticed some delay in writing when I did quick serial photography at 24MP. In contrast, my Z5C sometimes takes 30 seconds to save a single 8MP shot. Today I went from 100% to 41% battery within less than 4 hours, because apps regularly freeze and heat up the phone for 30-60 seconds when accessing the card. Changing tracks on Spotify takes 20 seconds on average. I did a test video recording (1080p 30fps) to SD card yesterday: stopping the recording after 30 seconds, the phone froze completely for 90 seconds, I could lock and unlock it but would always end up back in the frozen camera app, not even the system buttons were responding. In the end, the recording was actually 2 minutes long, but everything after 30 seconds was corrupted.

I don't assume that this is expected behaviour, I'm just trying to figure out what is the cause – the brand, the speed class, or a defective card. I will try returning the card under warranty tomorrow, because re-doing the SD card benchmark a while after formatting it, sustained write rates have dropped to sometimes under 5 MB/s, which clearly doesn't even fulfil the advertised Class 10 standard anymore.

[Uliwooly]

@Anamon2

You might have a faulty SD card or worst, a fake SD card, you might want to return/exchange it. 

[Anamon2 · Accepted solution]

Apparently, my card wasn't faulty, but the Ultra line of SanDisk SD cards are simly not suitable for smartphones. I have contacted SanDisk customer support, and this was their reply (translated by me, as the exchange was in German):

---

From the information you supplied, we gather that your card is causing malfunctions when it is inserted into your phone. We're sorry to hear this and apologise for the inconvenience.

But first, I'd like to inform you about something very important.

Your phone is a very powerful device. For the Xperia Z5 Compact, we recommend cards from the Extreme or even Extreme Pro lines. A simple Ultra card can not fulfil the requirements of the phone. This is why you are getting those delays, which you in turn do not notice with the Extreme card.

The Extreme card is a high-performance card that is suitable for your phone.

You should not get these issues from simple music playback, but please consider that this card is not "powerful" enough for the Xperia Z5 Compact.

---

They go on to suggest that I try formatting the card on Windows instead of Android, and then try again, which I'm going to try, but I don't have high hopes that it's going to change anything, considering the first part of the response.

So ultimately, it seems that the SD Speed Class 10, UHS-I cards of the Ultra line are not fast enough for modern smartphones. Despite the packaging claiming that it is perfectly suited for smartphones, and even carrying the picture of an Android phone. I'm pretty unhappy about that, because I would've had no problem going for the more expensive Extreme card, if the packaging had clearly stated that the card is not suitable for use in my phone.