patpro at patpro.net
Tue Dec 29 11:22:21 UTC 2009
On 29 déc. 2009, at 11:51, Ronald Klop wrote:
>>> That's certainly not the case with UFS snapshots, which can take a
>>> time to complete (we're talking freezing your machine's disk
>>> for many minutes), and are limited to 20 total.
>> UFS uses copy on write. But you say many minutes to complete? Don't
>> speak about dump(1), that uses snapshot as a basis to dump a live
>> I agree, UFS snapshot creation is not lightning-fast, but many
>> seems a lot to me, and I never experienced such a long creation time.
> As far as I know UFS snapshots need to create a list of currently in
> use blocks. This is O(n) on the size of the FS and pauses the FS
> during the snapshot. On large FS's this can take a long time.
> ZFS always maintains this list so it only needs to mark this list as
> readonly to create a snapshot. This is O(1).
That's a very interesting precision. Thank you.
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