I'm experimenting with using btrfs on my Debian Linux armhf system. The rfs is on a micro SD card. On bootup I get the message "Btrfs detected SSD devices, enabling SSD mode". What features does this SSD mode give me exactly?
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1 Answer
Traditional hard drives have a spinning disk platter. This means that filesystems can (and do) perform several optimizations. For example, it will locate segments of a file in a contiguous region of the disk, so that when you read different parts of the file, the kernel doesn't have to wait for the platter to spin to a different place. Another optimization done is to locate often-accessed files near each other. Again, this means that statistically, you will spend less time waiting for the disk platter to turn.
By definition, a solid-state drive doesn't have a spinning platter. This means that all of the optimizations done for spinning-platter devices are a dumb idea. All that SSD mode does is turn these optimizations off. Nothing to worry about.
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OK that is good to know. Do you happen to know what exactly happens when there's a checksum error when doing a read? From what I've read an error is logged, but is this returned to the calling application somehow? On my systems there is no human to read the logs. Commented Jun 2, 2014 at 3:44
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1Platters spin all the time and don't move. That's the disk head that needs to move upon a seek instead of reading what's just there. Commented Jun 2, 2014 at 6:19
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@StéphaneChazelas thanks for the correction; I'll update it in the morning– strugeeCommented Jun 2, 2014 at 7:41