On 05/05/2014 11:17 PM, Hugo Mills wrote:
[...]
> Does this all make sense? Are there any other options or features
> that we might consider for chunk allocation at this point?
The kind of chunk (DATA, METADATA, MIXED....) and the subvolume (when /if this
possibility will come)
As how write this information I suggest the following options:
-[DATA|METADATA|MIXED|SYSTEM:]NcMsPp[:<driveslist>[:/subvolume/path]]
Where <drivelist> is an expression of the disks policy allocation:
a)
{sdX1:W1,sdX2:W2...}
where sdX is the partition involved and W is the weight:
#1 {sda:1,sdb:1,sdc:1} means spread all the disks
#2 {sda:1,sdb:2,sdc:3} means linear from sda to sdc
#3 {sda:1,sdb:1,sdc:2} means spread on sda and sdb (grouped)
then (when full) sdc
or
b)
#1 (sda,sdb,sdc) means spread all the disks
#2 [sda,sdb,sdc] means linear from sda to sdc
#3 [(sda,sdb),sdc] means spread on sda and sdb (grouped)
then (when full) sdc
or
c)
#1 (sda,sdb,sdc) means spread all the disks
#2 sda,sdb,sdc means linear from sda to sdc
#3 (sda,sdb),sdc means spread on sda and sdb (grouped)
then (when full) sdc
Some examples:
- 1c2s3b
Default allocation policy
- DATA:2c3s4b
Default allocation policy for the DATA
- METADATA:1c4s:(sda,sdb,sdc,sdd)
Spread over all the 4 disks for metadata
- MIXED:1c4s:sda,sdc,sdb,sdd
Linear over the 4 disks, ordered as the list for
Data+Metadata
- DATA:1c4s:(sda,sdc),(sdb,sdd)
spread over sda,sdc and then when these are
filled, spread over sdb and sdc
- METADATA:1c4s:(sda,sdb,sdc,sdd):/subvolume/path
Spread over all the 4 disks for metadata belonging the
subvolume /subvolume/path
I think it would be interesting to explore some configuration like
- DATA:1c:(sda)
- METADATA:2c:(sdb)
if sda is bigger and sdb is faster
Some further thoughts:
- more I think about the allocation policy per subvolume and/or file basis and
more I think that it would be a messy to manage
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