THIN-PROVISIONING WITH SNAPSHOT TECHNOLOGY

• US 20040230766A1
• Filed: 05/07/2004
• Published: 11/18/2004
• Est. Priority Date: 05/12/2003
• Status: Active Grant

• Current Assignee: Hewlett Packard Enterprise Development LP (Hewlett-Packard Enterprise Company)
• Original Assignee: 3pardata Incorporated
• Inventors: Cameron, Douglas J.
• Granted Patent: US 6,823,442 B1
• Time in Patent Office: Days
• US Class Current: 711/203
• CPC Class Codes: G06F 3/0605 by facilitating the interaction with a user or administrator
• CPC Class Codes: G06F 3/0665 at area level, e.g. provisioning of virtual or logical volumes
• CPC Class Codes: G06F 3/0689 Disk arrays, e.g. RAID, JBOD

Abstract

A method is provided to allow a system administrator of a utility storage server to provision virtual volumes several times larger than the amount of physical storage within the storage server. A virtual volume is a virtual representation of multiple disks as a single large volume to a host or an application. In one embodiment, a virtual volume comprises an exception list containing the set of differences from dummy base volume consisting of all zeros. This exception list can be made up of address tables that map virtual volume pages to logical disk pages. As storage demand grows, additional storage is allocated for the address tables and the data pages from separate pools of storage. If any of the pools runs low, more logical disk regions are allocated to that pool.

Claims

1. A method for writing to a virtual volume mapped to a logical disk, comprising:

receiving a request to write a data to the virtual volume at an address;

traversing a first table representing the virtual volume to find a first pointer at a first offset based on a first portion of the address, the first pointer leading to one of a plurality of second tables (“

said one second table”

) also representing the virtual volume;

following the first pointer to said one second table;

traversing said one second table to find a second pointer at a second offset based on a second portion of the address, the second pointer leading to one of a plurality of third tables (“

said one third table”

);

if said one second table does not exist,

determining if the number of available table pages in a first pool is less than a first threshold;

if the number of available table pages in the first pool is not less than the first threshold,

allocating one table page from the first pool to form said one second table;

writing the first pointer at the first offset in the first table;

if the number of available table pages in the first pool is less than the first threshold,

requesting additional table pages to be added to the first pool.

2. The method of claim 1, further comprising:

if the number of available table pages in the first pool is less than the first threshold,

requesting additional table pages to be added to the first pool;

determining if the additional table pages have been added before timing out;

if the additional table pages have been added before timing out,

allocating one table page from the first pool to form said one second table;

writing the first pointer at the first offset in the first table;

if the additional table pages have not been added before timing out, returning a write failure message.

3. The method of claim 2, further comprising:

following the second pointer to said one third table;

traversing said one third table to find a third pointer at a third offset based on a third potion of the address, the third pointer leading to one of a plurality of data pages (“

said one data page”

);

if said one third table does not exist,

determining if the number of available table pages in the first pool is less than the first threshold;

if the number of available table pages in the first pool is not less than the first threshold,

allocating one table page from the first pool to form said one third table;

writing the second pointer at the second offset in the second table.

4. The method of claim 3, further comprising:

if the number of available table pages in the first pool is less than the first threshold,

requesting additional table pages to be added to the first pool;

determining if the additional table pages have been added before timing out;

if the additional table pages have been added before timing out,

allocating one table page from the first pool to form said one third table;

writing the second pointer at the second offset in the second table;

if the additional table pages have not been added before timing out, returning the write failure message.

5. The method of claim 4, further comprising:

following the third pointer to said one data page;

writing the data to said one data page at a fourth offset based on a fourth portion of the address and returning a write pass message;

if said one data page does not exist,

determining if the number of available data pages in a second pool is less than a second threshold;

if the number of available data pages in the second pool is not less than the second threshold,

allocating one data page from the second pool to form said one data page;

writing the third pointer at the third offset in the third table;

writing the data to said one data page at the fourth offset and returning the write pass message.

6. The method of claim 5, further comprising:

if the number of available data pages in the second pool is less than the second threshold;

requesting additional data pages to be added to the second pool;

determining if the additional data pages have been added before timing out;

if the additional data pages have been added before timing out,

allocating one data page from the second pool to form said one data page;

writing the third pointer at the third offset in the third table;

writing the data to said one data page at the fourth offset and returning the write pass message;

if the additional data pages have not been added before timing out, returning the write failure message.

7. The method of claim 6, in response to said requesting additional table pages to be added to the first pool or said requesting additional data pages to be added to the second pool,

retrieving an allocation control structure associated with the requesting virtual volume, the allocation control structure comprising a first maximum physical allocation for the virtual volume, a second maximum physical allocation for a group of virtual volumes including the virtual volume, a first warning point on the first maximum physical allocation, a second warning point on the second maximum physical allocation, and RAID parameters controlling the creation of additional logical disk storage;

determining if the virtual volume is greater than the first maximum physical allocation;

if the virtual volume is greater than the first maximum physical allocation, issuing an allocation failure alert and terminating the allocation request processing.

8. The method of claim 7, further comprising,

if the virtual volume is not greater than the first maximum physical allocation,

determining if the logical disk has one storage unit (“

logical disk region”

) available;

if the logical disk has one logical disk region available,

dividing said one logical disk region into table or data pages;

allocating the table or data pages to the first or the second pool;

updating a system table of contents to record the allocation of said one logical disk region to the virtual volume;

determining if the virtual volume is greater than the first warning point;

if the virtual volume is greater than the first warning point, issuing an allocation warning alert.

9. The method of claim 8, further comprising:

if the logical disk does not have one logical disk region available,

determining if the group of virtual volumes is greater than the second maximum physical allocation;

if the group of virtual volume is greater than the second maximum physical allocation, issuing an allocation failure alert and terminating the allocation request processing.

10. The method of claim 9, further comprising:

if the virtual volume is not greater than the second maximum physical allocation,

creating a new logical disk;

determining if the group of virtual volumes is greater than the second warning point;

if the group of virtual volumes is greater than the second warning point,

issuing an allocation warning alert;

dividing a logical disk region from the new logical disk into table or data pages;

allocating the table or data pages to the first or the second pool; and

updating a system table of contents to record the allocation of the logical disk region to the virtual volume.

11. The method of claim 1, wherein the virtual volume is distributed amongst a system of nodes, the method further comprising replicating the data to another node in the system.

12. A method for provisioning a virtual volume mapped to a logical disk, comprising:

receiving a request to write a data to the virtual volume at an address;

traversing a table representing the virtual volume to find a pointer at an offset based on a portion of the address, the pointer leading to one of a plurality of data pages (“

said one data page”

);

if said one data page does not exist,

determining if the number of available data pages in a pool is less than a threshold;

if the number of available data pages in the pool is less than the threshold,

requesting additional data pages to be added to the pool;

determining if the logical disk has one storage unit (“

logical disk region”

) available;

if the logical disk has one logical disk region available,

dividing said one logical disk region into data pages;

allocating the data pages to the pool.

13. The method of claim 12, further comprising:

if the logical disk does not have one logical disk region available,

creating a new logical disk;

dividing a logical disk region from the new logical disk into data pages;

allocating the data pages to the pool.

14. The method of claim 13, further comprising:

if the number of available data pages in the pool is not less than the threshold,

allocating one data page from the pool to form said one data page;

writing the data to said one data page at the offset based on another portion of the address and returning a write pass message.

15. The method of claim 12, in response to said requesting additional data pages to be added to the pool, further comprising:

issuing an allocation failure alert if the virtual volume is greater than a limit point on maximum physical allocation.

16. The method of claim 15, in response to said requesting additional data pages to be added to the pool, further comprising:

issuing an allocation warning alert if the virtual volume is greater than a warning point on maximum physical allocation, the warning point being less than the limit point.

17. The method of claim 12 in response to said requesting additional data pages to be added to the pool, further comprising:

issuing an allocation failure alert if a group of virtual volume is greater than a limit point on maximum physical allocation.

18. The method of claim 17, in response to said requesting additional data pages to be added to the pool, further comprising:

issuing an allocation warning alert if a group of virtual volumes including the virtual volume is greater than a warning point on maximum physical allocation, the warning point being less than the limit point.