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dman777
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NeddySeagoon
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 Posted: Tue Jun 28, 2016 10:45 pm Post subject: |
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dman777,
Trim is a background operation. NCQ Trim is not useful as the there is no hurry for the trim to complete and no time to be saved.
The trim command may go in the NCQ queue but the drive will only make a note of it.
When some space it trimmed, its up to the drive when it actually does the erase.
There are advantages and disadvantages in waiting, depending on how full the device is (when will the space be needed) to trimming too often and incurring extra writes as a result.
The drives erase block size is much larger than the write block size, so any data in the block about to be erased that isn't being trimmed, needs to be moved.
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NeddySeagoon
Computer users fall into two groups:-
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dman777
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| Posted: Wed Jun 29, 2016 3:04 am Post subject: |
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Hmm.... this contradicts what I read in the wikipedia, so I am probably misunderstanding....
https://en.wikipedia.org/wiki/Trim_(computing)#Shortcomings
| Quote: | | The non-queued nature of the command requires the driver to first wait for all outstanding commands to be finished, issue the TRIM command, then resume normal commands. ...This penalty can be minimized in solutions that periodically do a batched TRIM, rather than trimming upon every file deletion, by scheduling such batch jobs for times when system utilization is minimal. |
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NeddySeagoon
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| Posted: Wed Jun 29, 2016 4:24 pm Post subject: |
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dman777,
I know of one user who was able to recover data from a deleted file, several days after it was trimmed.
This is anecdotal evidence of one user and one drive.
This particular drive did not appear to be in a hurry to perform the erase operation that it was authorised to do.
Drives will vary.
Performing the erase as soon as its indicated leads to as increased number of writes, that shorten drive life.
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NeddySeagoon
Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail. |
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Kernel & Hardware
