On 9/11/06, Matthew Ahrens <[EMAIL PROTECTED]> wrote:
James Dickens wrote: > On 9/11/06, Matthew Ahrens <[EMAIL PROTECTED]> wrote: >> B. DESCRIPTION >> >> A new property will be added, 'copies', which specifies how many copies >> of the given filesystem will be stored. Its value must be 1, 2, or 3. >> Like other properties (eg. checksum, compression), it only affects >> newly-written data. As such, it is recommended that the 'copies' >> property be set at filesystem-creation time >> (eg. 'zfs create -o copies=2 pool/fs'). >> > would the user be held acountable for the space used by the extra > copies?Doh! Sorry I forgot to address that. I'll amend the proposal and manpage to include this information... Yes, the space used by the extra copies will be accounted for, eg. in stat(2), ls -s, df(1m), du(1), zfs list, and count against their quota. > so if a user has a 1GB quota and stores one 512MB file with > two copies activated, all his space will be used? Yes, and as mentioned this will be reflected in all the space accounting tools. > what happens if the > same user stores a file that is 756MB on the filesystem with multiple > copies enabled an a 1GB quota, does the save fail? Yes, they will get ENOSPC and see that their filesystem is full. > How would the user > tell that his filesystem is full since all the tools he is used to > report he is using only 1/2 the space? Any tool will report that in fact all space is being used. > Is there a way for the sysdmin to get rid of the excess copies should > disk space needs require it? No, not without rewriting them. (This is the same behavior we have today with the 'compression' and 'checksum' properties. It's a long-term goal of ours to be able to go back and change these things after the fact ("scrub them in", so to say), but with snapshots, this is extremely nontrivial to do efficiently and without increasing the amount of space used.) > If I start out 2 copies and later change it to on 1 copy, do the > files created before keep there 2 copies? Yep, the property only affects newly-written data. > what happens if root needs to store a copy of an important file and > there is no space but there is space if extra copies are reclaimed? They will get ENOSPC.
though I think this is a cool feature, I think i needs more work. I think there sould be an option to make extra copies expendible. So the extra copies are a request, if the space is availible make them, if not complete the write, and log the event. It the user really requires guaranteed extra copies, then use mirrored or raided disks. It seems just to be a nightmare for the administrator, you start with 3 copies and then change to 2 copies, you will have phantom copies that are only known to exist to the OS, it won't show in any reports, zfs list doesn't have an option to show which files have multiple clones and which dont. There is no way to destroy multiple clones without rewriting every file on the disk. James
> Will this be configurable behavior? No. --matt
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