topic Re: Write speed from PC to XZP's SD-card over USB3.0 SD-card... in XZ Series

[Bug] SD card access speed is only 7Mb/s when encryption is enabled

pribambas — Tue, 15 Aug 2017 16:07:04 GMT

I use Samsung EVO+ microSDXC 256GB card. When SD card encryption is activated in Settings, read/write access speed to the SD card is about 7Mb/s which is too slow. Without SD card encryption I got 40Mb/s for write and 70Mb/s for read and these speeds are rather acceptable. How can I get at least 40Mb/s with enabled encryption?

I tested speeds by copying a 1Gb file from the internal storage to the SD card and back. I tried several file managers from Play and also ADB shell:
time cp /storage/emulated/0/1gbfile /storage/0D49-786B/

Needless to say that the internal storage is also encrypted and nevertheless it's very fast. I guess a hardware acceleration might be missed for SD encryption, but 7Mb/s is slow even for pure software implementation. Please invite a kernel dev representative to the thread. Thanks.

Anybody from Sony devs. Couldn't you explain why is encry...

pribambas — Thu, 17 Aug 2017 15:24:11 GMT

Anybody from Sony devs. Couldn't you explain why is encrypted SD card access is so slow? Are there any plans to fix this? Thanks.

Write speed from PC to XZP's SD-card over USB3.0 SD-card...

pribambas — Sun, 20 Aug 2017 21:40:57 GMT

Write speed from PC to XZP's SD-card over USB3.0

SD-card encryption enabled: 8.8Mb/s

SD-card encryption disabled: 31Mb/s

Re: Write speed from PC to XZP's SD-card over USB3.0 SD-card...

Qatrium — Mon, 21 Aug 2017 05:02:01 GMT

@pribambas

I'm not a dev, but logically there's nothing wrong with the symptoms you're describing. An encrypted SD card will be slower on file transfer as it's reading + encrypting + writing at the same time. So the encryption process is what is taking the extra time.

Re: Write speed from PC to XZP's SD-card over USB3.0 SD-card...

pribambas — Mon, 21 Aug 2017 06:12:26 GMT

@Quester

First of all 31Mb/s of unencrypted access is too slow for a SD card that shows 70Mb/s of real write speed on another device. It seems to me there is a hardware bottleneck in XZP that couldn't be fixed by software updates. Ok, I don't expect a fix for unencrypted write speed.

But with modern hardware encryption engines we may expect speeds of tens or even hundreds megabytes per second. So I expect encrypted write speed to be at least not lower than the unencrypted one. Even 6-years old marvell chips for NAS were able to do AES with 10Mb/s.

Moreover internal storage is also encrypted, but it's still much faster than even unencrypted SD-card.

So there is something to fix with SD-card encryption and I expect a software update from Sony that will fix it.

Re: Write speed from PC to XZP's SD-card over USB3.0 SD-card...

najodleglejszy — Mon, 21 Aug 2017 06:44:01 GMT

internal storage is fast despite being encrypted because of the CPU being specifically made to support encryption (as required by Google). before that was a thing, encrypting your device resulted in a performance hit. perhaps it's that kind of an issue with the external storage.

Re: Write speed from PC to XZP's SD-card over USB3.0 SD-card...

pribambas — Mon, 21 Aug 2017 06:57:51 GMT

@najodleglejszy wrote:
the CPU being specifically made to support encryption

Yes, but nothing stops Sony or any other vendor from using this CPU/hardware assistance for encrypting SD card, SSL or VPN traffic or anything else. There may be a limited number of hardware-assisted encryption/hashing algorithms, but why not selecting an assisted algorithm for SD card?

Re: [Bug] SD card access speed is only 7Mb/s when encryption is enabled

pribambas — Wed, 13 Sep 2017 10:14:42 GMT

45.0.A.7.137

I've retested. About 10Mb/s copying from internal storage to SD card. Still tooooo slow

Re: [Bug] SD card access speed is only 7Mb/s when encryption is enabled

pribambas — Wed, 11 Oct 2017 15:42:17 GMT

Sony, are you going to fix slow SD card encryption?

Re: [Bug] SD card access speed is only 7Mb/s when encryption is enabled

pribambas — Mon, 23 Oct 2017 11:21:24 GMT

The oreo update (47.1.A.3.254) didn't fix the SD card encryption speed issue. It's still too slow 7-10Mb/s read/write for a high performance UHS-I card.