Re: I/O errors while writing to external Transcend XS-2000 4TB SSD

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On Thu, Feb 15, 2024 at 12:09:20PM +0100, Martin Steigerwald wrote:
> Kent Overstreet - 12.02.24, 21:42:26 CET:
> 
> [thoughts about whether a cache flush / FUA request with write caches 
> disabled would be a no-op anyway]
> 
> > > I may test the Transcend XS2000 with BTRFS to see whether it makes a
> > > difference, however I really like to use it with BCacheFS and I do not
> > > really like to use LUKS for external devices. According to the kernel
> > > log I still don't really think those errors at the block layer were
> > > about anything filesystem specific, but what  do I know?
> > 
> > It's definitely not unheard of for one specific filesystem to be
> > tickling driver/device bugs and not others.
> > 
> > I wonder what it would take to dump the outstanding requests on device
> > timeout.
> 
> I got some reply back from Transcend support.
> 
> They brought up two possible issues:
> 
> 1) Copied to many files at once. I am not going to accept that one. An 
> external 4 TB SSD should handle writing 1,4 TB in about 215000 files, 
> coming from a slower Toshiba Canvio Basics external HD, just fine. About 
> 90000 files was larger files like sound and video files or installation 
> archives. The rest is from a Linux system backup, so smaller files. I 
> likely move those elsewhere before I try again as I do not need these on 
> flash anyway. However if the amount of files or data matters I could never 
> know what amount of data I could write safely in one go. That is not 
> acceptable to me.
> 
> 2) Power management related to USB port. Cause I am using a laptop. It may 
> have been that the Linux kernel decided to put the USB port the SSD was 
> connected to into some kind of sleep state. However it was a constant 
> rsync based copy workload. Yes, the kernel buffers data and the reads from 
> Toshiba HD should be quite a bit slower than the Transcend SSD could 
> handle the writes. I saw now more than 80-90 MiB/s coming from the hard 
> disk. However I would doubt this lead to pauses of write activity of more 
> than 30 seconds. Still it could be a thing.
> 
> Regarding further testing I am unsure whether to first test with BTRFS on 
> top of LUKS – I do not like to store clear text data on the SSD – or with 
> BCacheFS plus fixes which are 6.7.5 or 6.8-rc4 in just in the case the flush 
> handling fixes would still have an influence on the issue at hand.
> 
> First I will have a look on how to see what USB power management options 
> may be in place and how to tell Linux to keep the USB port the SSD is 
> connected to at all times.
> 
> Let's see how this story unfolds. At least I am in no hurry about it.

This may not be an issue of power management but rather one of 
insufficient power.  A laptop may not provide enough power through its 
USB ports for the Transcend SSD to work properly under load.

You can test this by connecting a powered UBS-3 hub between the laptop 
and the drive.

Alan Stern




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