Extreme 1TB SSD transfer speed very slow then spurts of fast

Internal SSD Ultra® 3D SSD
1

I have a SanDisk Extreme 1TB portable SSD, I use for backups of my computers. Normally I am transferring files of 50MB to 15GB and the disk transfers at a rate between 4-5MB/s up to ~250MB/s and take just a few minutes. Lately I’ve been transferring larger files up to 120GB. These have been transferring at a rate between 250KB/s up to ~340MB/s but staying primarily in the 200KB/s to 20MB/s range and the transfers have taken about an hour to complete.

I back up a desktop and 3 laptops, all running Windows 10 or 11, 64 bit. All are updated, scanned and backed up weekly. I am using the USB C cable that came with the drive with an adapter for two laptops with USB B ports.

I am doing the desktop now and it is running predominately in the 200KB/s to 18MB/s range. I used Task Manager to close as many unnecessary programs and processes as possible with no apparent difference. I notice in TM that there is a COM Surrogate process that is running at ~25% of CPU and rated Very High for power usage. I don’t know if there is any correlation to the transfer speed.

I’d love to see the SSD run at much closer to it’s rated speed of up to 400MB/s.

Thanks

1 Like
2

… I’d love to see the SSD run at much closer to it’s rated speed of up to 400MB/s.

Actually, I just noticed, the Dashboard app that comes with this SSD says this disk has a transfer speed of up to 6GB/s! I’d settle for a 10th of that. Thanks

3

Can anyone out there suggest any fixes?

4

I’m sorry I can’t report any promising fixes for this. I’ve been trying to figure out what is going on for a month or so. My external /portable SSD drive is behaving similarly (although it’s not SanDisk). I will post everything I’ve found so far in the hopes that it helps us or someone in future.

Reproduce: Plug in drive (using proper USB-C cable that came with drive, or certified “USB 4” cable). Transfer a file (~5 GB MKV video file, via Windows Explorer). File transfers very slowly, around 2 MB/s according to Explorer (confirmed via Crystal DiskMark). Surprise: After a few minutes it will rocket up to full speed (on my PC with USB 3 that means around 300 MB/s). Surprise again: After a few more transfers, the drive WILL sustain maximum write speeds consistently (until disconnected, then this will start again).

Notes: This drive has working perfectly for a year or so, was always operating at max speeds. It is 70-80% full (movies backup). Drive file system is exFAT. Safely handled and stored at home the entire time (only plugged in for backups, under an hour per month or so). Drive firmware updated (Samsung T7 Shield 2TB via Magician). Updated mobo drivers (AMD chipset on ASUS B450). Restarted many times, even unplugged for hard restart (latest Windows 11 Pro). Tried different cables, ports, files, but same result. Tested disabling Windows Security (esp. real-time protection), no change. Doesn’t seem like failing drive (diagnostics, SMART, temps all fine).

More: Not tried enabling “write caching” for drive, because of data loss risks, and it previously worked fine without. Not tried defragmenting (exFAT, SSD). Have not tried other PC. I’ve not contacted manufacturer for support or replacement (yet). I’ve only had one portable drive (HDD) have problems, amazingly fixed just by increasing free space and defrag (probably unrelated).

TL;DR: I’m leaning towards problem originating from Windows (update) or motherboard (driver chipset, BIOS). Maybe free space? Maybe file system (exFAT, Windows again)? Bizarre.

Update: I’ve settled on this being a free space issue. Even though I could not find a satisfactory amount data to confirm with certainty. Bought larger drive, copied data, formatted old drive (“secure erase” SSD is instant via Magician, NTFS/GPT via AOMEI Disk Assistant); Speeds seem normal again, will still use but for less demanding task.

New guidelines I will follow: Do not fill drives over 80% (both SSD or HDD, remove unnecessary data, if impossible buy double capacity drive). Stick with NTFS file system (not exFAT, unnecessary on Windows/Linux, not especially robust).

1 Like
5

The slow transfer speeds on your SanDisk SSD may be due to the COM Surrogate process, which handles file previews and is using high CPU. Try disabling file thumbnails in File Explorer to reduce this load. Also, ensure your USB-C cable and adapter are functioning properly, check the SSD’s health, update USB drivers and SSD firmware, and try toggling write caching in Device Manager to improve performance.