Score:-1

How do I force a Samsung 870 QVO drive to flush its SLC cache?

ph flag

I have 16 Samsung 870 QVO 8TB drives in mdraid 0 (striped) with XFS on top. Rocky Linux 8. Mixed read/write load, read volume over 100x write. Since so little is written I thought I could use these drives and save money without sacrificing performance. I bought them under the assumption that they would slowly empty their SLC cache to QLC. Instead, apparently they wait until idle and then flush it all at once (cite). Or, since they are never idle in my server, they flush whenever their cache is full and torpedo performance of the whole array.

I'm wondering if there is a way for me to command the drives to flush their SLC cache to QLC. That way I could flush say every hour instead of every few weeks. sync doesn't do it.

Incidentally, I tried running fstrim on the filesystem. Very strange result. Each time I run fstrim -v it takes hours and then reports having trimmed all free space, something like 27 TB. Fewer than 100 GB written during this time. Seems to be the same problem reported here and here with no solution.

djdomi avatar
za flag
what are you trying to do or solve with your question? Is it business related?
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