| Issue 71: | Supporting Multiple OHSM on the system | |
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ext3Yaan enhancement: After successful completion of ext3Yaan phase 1 we will start with supporting mount points and OHSMs in a system
Mar 7, 2009
Project Member
#1
sandeepksinha
Mar 7, 2009
RKS/Vineet if you guys have any ideas how we can implement this, kindly list it here. I have thought of a couple of them, will update on this soon.
Mar 7, 2009
SKS once said that we will modify the superblock of ext2/3 Thus it will have one pointer to a structure. That structure will have the pointers to all the policies for that particular mounted FS. Whenever we need the policies we can access that pointer.
Mar 11, 2009
Hi all, Feeling quiet okay, but still in bed rest, some cells from my blood have gone missing, running fsck to recover. ;) We require different policy data structures for different instances of file system. Every superblock has a its mount point or volume name stored in it. So we can specify different policy files along with the mount points or volume name where we want to apply these policies. Also different sam tables for different mount points. So we need to add a mount point or volume name to our policy data structures. Just check the mount point or volume name from the superblock during allocation and relocation, and refer corresponding policy. This would prevent changing the superblock structure. See if you guys have a better idea, but i feel that we should not change the superblock.
Mar 11, 2009
Dude lets mark this for 2.0 and work on making 1.0 more concrete and robust. We have to mak eour current system more robust.
Labels:
target-Release2.0
Jul 14, 2009
Changing the owner to Vineet Priority to High Status to In Progress
Status:
In-progress
Owner: checkout.vineet Labels: -Priority-Medium Priority-High
Jul 14, 2009
Can please SKS throw some light on the issue.
Owner:
sandeepksinha
Jul 14, 2009
The issue here is to support multiple mount points. So we can have multiple OHSMs in single system, We need to maintain seperate SAM table for each individual OHSM enabled at different mount points.
Jul 15, 2009
its not only the SAM table but all the data structures. We mneed to add a pointer to super block ( may be there is some unused reserved space) or we can maintain a global table for all the OHSM.
Jul 15, 2009
Hi Rohit,
I think you should actually thank me for this :)
Now, we have been able to completely boil down every instance of OHSM to have just
four structures and a couple of pointers.
So, what we can typically do is to have a structure something like,
struct ohsm_instance{
void* super_block_pointer;
void* incore_super_block_pointer;
int sam[X][Y];
struct ohsm_tier_device_info *dev_info;
struct ohsm_allocation_policy *allocpol;
struct ohsm_relocation_policy *relocpol;
Some locks and other members;
};
This would probably suffice all of our needs.
Here we can have the super_block_pointer as the primary key, which will differentiate
between the different instances, while searching.
Since, we don't have have those "72" data structures and tables, we are at a better
position now.
I think you should take this work forward.
We will have to make the code modular at this stage only before it becomes more
complex. Already I can see a lot happening.
Jul 15, 2009
I am already thankful, ;) |