Mastodawn

Ok, so due to my storage problems I have talked with family and someone gave me a NAS drive they weren't using. (It's basically new. Like 40 hours of use.) I have it in a drive bay that can be turned off so I don't have to listen to it spinning (though honestly it's the least annoying mechanical drive I've ever had.) I still want to keep it off when I'm not using it (most of the time,) hoping it will last that much longer.

Besides the obvious unmounting mounted partitions, what's the safest, best way to "remove" a drive in Linux before actually powering it off? I want to be sure all writes (even filesystem stuff) are done and the drive is ready for safe removal, but of course the computer sees a SATA drive as "internal."

No I'm not buying an enclosure.

#Linux #Harddrives #Storage

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Nazo Feb 28

Right now what I'm doing is:

sudo hdparm -Y /dev/[device]
echo 1 | sudo tee /sys/block/[device]/device/delete

Based on some initial searching.

The hdparm -Y issues a "sleep" command and then the "delete" is supposed to remove it from the listing so it won't be polled. I do this manually (from a script for now) but I'd really like something more optimized for device removal (eg ensuring all writes to the device have stopped and etc even before issuing the command.)

Plus it would be super nice if I didn't have to find out which devicename it's using each time. (I have other removable devices after all, so it's not guaranteed to always be the same letter.) Maybe I could do a UUID or something for the disk itself?

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Scott VE3QBZ Feb 28

@nazokiyoubinbou mounting the drive with the sync option will help - forces all writes to be committed immediately rather than buffered.

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Nazo Feb 28

@scott That's a good idea, thanks.

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Nazo

@scott Ok, mounting with sync caused the drive to thrash. A lot. On a quite slow transfer... (I was downloading something from my server — not even a transfer from another filesystem.) So I guess sync isn't so great for a magnetic drive. Switching back to asynchronous made it go nearly silent. I guess it's able to order the writes better or something.

Hopefully the other suggestion will cover both bases sufficiently. I also tossed in a plain sync command to the mounted location before doing any of the rest of that stuff, so hopefully between all this I can be fairly certain. (Probably blockdev --flushbufs is the key thing though. This is just for good measure.)

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Scott VE3QBZ Mar 1

@nazokiyoubinbou yup, synchronous mode is quite slow :)

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Nazo Mar 1

@scott It wasn't just slow. I expected it to be slow. Unbuffered being slower overall is a given.

It's the thrashing that bothered me. That sound means the head is having to move quite a lot. Which... didn't make sense. This was for a mere 6MB/s or so (the drive was limiting my download rate! The server is kind of slow — 11 or so is its max — and it limited it to about 6-7.) I remounted with async and hit resume and suddenly it goes almost dead silent and flares up to full speed. I hit sync and all that immediately after and there was basically nothing buffered. (This was with Filezilla which just doesn't use a lot of buffering.)

I can't really explain it. I just guess that the writes weren't well ordered when synced somehow. This was with btrfs though. Maybe it's the culprit.