Host-based virtualization optimizations in storage environments employing off-host storage virtualization

• US 20060112251A1
• Filed: 06/20/2005
• Published: 05/25/2006
• Est. Priority Date: 11/26/2003
• Status: Active Grant

• Current Assignee: Veritas Technologies, LLC (Whitehouse Group Ltd.)
• Original Assignee: Veritas Operating Corporation (Gen Digital Inc.)
• Inventors: Karr, Ronald S., Bezbaruah, Angshuman, Guha, Amitava
• Granted Patent: US 7,669,032 B2
• Time in Patent Office: Days
• US Class Current: 711/170
• CPC Class Codes: G06F 11/201 between storage system components
• CPC Class Codes: G06F 11/2089 Redundant storage control functionality
• CPC Class Codes: G06F 2206/1012 Load balancing
• CPC Class Codes: G06F 3/061 Improving I/O performance
• CPC Class Codes: G06F 3/0635 by changing the path, e.g. traffic rerouting, path reconfiguration
• CPC Class Codes: G06F 3/0662 Virtualisation aspects
• CPC Class Codes: G06F 3/067 Distributed or networked storage systems, e.g. storage area networks [SAN], network attached storage [NAS]

Abstract

A system for host-based virtualization optimizations in storage environments employing off-host virtualization may include a host, one or more physical storage devices, and an off-host virtualizer such as a virtualizing switch. The off-host virtualizer may be configured to aggregate storage within the one or more physical storage devices into a virtual storage device such as a logical volume, and to provide control data for the virtual storage device to the host. The host may be configured to use the control data to perform a function in response to an I/O request from a storage consumer directed at the virtual storage device, and to use a result of the function to coordinate one or more I/O operations corresponding to the I/O request.

Claims

1. A system comprising:

a host;

one or more physical storage devices; and

an off-host virtualizer;

wherein the off-host virtualizer is configured to;

aggregate storage within the one or more physical storage devices into a virtual storage device; and

provide control data for the virtual storage device to the host;

wherein the host is configured to;

perform a function dependent on the control data in response to an I/O request targeted at the virtual storage device; and

use a result of the function to coordinate one or more I/O operations corresponding to the I/O request.

2. The system as recited in claim 1, wherein the off-host virtualizer includes a virtualizing switch.

3. The system as recited in claim 1, wherein the one or more physical storage devices include a first and a second physical storage device, and wherein the function comprises:

a detection that the I/O request requires access to the first physical storage device and the second physical storage device; and

a partition of the I/O request into a first physical I/O request targeted at the first physical storage device and a second physical I/O request targeted at the second physical storage device.

4. The system as recited in claim 1, wherein the host is further configured to send a request for an I/O operation of the one or more I/O operations to the off-host virtualizer.

5. The system as recited in claim 1, wherein the control data includes network path information.

6. The system as recited in claim 5, wherein the function includes a selection of a first preferred network path to access a first physical storage device of the one or more physical storage devices.

7. The system as recited in claim 6, further comprising two or more host bus adapters, wherein the first preferred network path includes a preferred host bus adapter of the two or more host bus adapters.

8. The system as recited in claim 6, further comprising two or more switches, wherein the first preferred network path includes a preferred switch of the two or more switches.

9. The system as recited in claim 6, wherein the host is further configured to select a second preferred network path to access the first physical storage device upon a detection of a triggering condition.

10. The system as recited in claim 9, wherein the triggering condition is a load imbalance detected in accordance with a load balancing policy.

11. The system as recited in claim 9, wherein the triggering condition is a path failure.

12. The system as recited in claim 9, wherein the first preferred network path includes a switch with a cache, and wherein, upon the selection of the second preferred network path, the host is further configured to coordinate a cache cleanup at the switch.

13. The system as recited in claim 9, wherein the triggering condition is a reception of a particular error code from the off-host virtualizer, wherein the particular error code includes an indication of an availability of the second preferred network path to the first physical storage device upon a detection of a failure along the first preferred network path.

14. The system as recited in claim 13, wherein, in response to the reception of the particular error code, the host is further configured to generate one or more retry attempts to access the first physical storage device.

15. The system as recited in claim 9, wherein the off-host virtualizer is further configured to:

send a particular error code to the host upon a detection of a failure along the first preferred network path during an I/O operation targeted at the first physical storage device;

wherein the host is further configured to;

send a query to the off-host virtualizer requesting an indication of an existence of an alternate network path to the first physical storage device;

wherein the off-host virtualizer is further configured to;

respond to the query by sending a reply to the host indicating that the first physical storage device is accessible via the second preferred network path;

and wherein the triggering condition is a reception of the reply by the host.

16. The system as recited in claim 1, wherein the virtual storage device is a mirrored logical volume including a first and a second mirror, wherein the off-host virtualizer is further configured to:

send a particular error code to the host upon a detection of a read error in response to a first read request targeted at the first mirror;

wherein the host is further configured to;

issue a second read request targeted at the second mirror in response to a reception of the particular error code.

17. The system as recited in claim 1, wherein the virtual storage device is a mirrored logical volume including a first and a second mirror, wherein the off-host virtualizer is further configured to:

send a particular error code to the host upon a detection of a read error in response to a first read request targeted at a first block of the first mirror;

wherein the host is further configured to;

send a query to the off-host virtualizer requesting an indication of an existence of an alternate redundant copy of the first data block in response to a reception of the particular error code;

wherein the off-host virtualizer is further configured to;

respond to the query by sending a reply to the host indicating that the second mirror contains an alternate redundant copy of the first data block;

and wherein the host is further configured to;

issue a second read request targeted at the alternate redundant copy at the second mirror in response to a reception of the reply.

18. The system as recited in claim 1, wherein a network path to the one or more physical storage devices comprises a first and a second switch, wherein the I/O request is a write request, and wherein the off-host virtualizer is further configured to:

divide a virtual address space of the virtual storage device into a first partition and a second partition;

designate the first switch as a first write coordinator to coordinate write operations for the first partition, and the second switch as a second write coordinator to coordinate write operations for the second partition;

wherein the control data includes an identification of the first and second write coordinators and the corresponding partitions; and

wherein the function includes a selection of a target write coordinator corresponding to the write request and a transmission of the write request to the target write coordinator.

19. The system as recited in claim 1, wherein the function includes a loading of configuration information associated with the virtual storage device at the off-host virtualizer.

20. The system as recited in claim 1, wherein the function includes an update to a dirty region log (DRL).

21. A method comprising:

aggregating storage within one or more physical storage devices into a virtual storage device at an off-host virtualizer;

providing control data for the virtual storage device to a host;

performing a function dependent on the control data at the host in response to an I/O request targeted at the virtual storage device; and

using a result of the function to coordinate one or more I/O operations corresponding to the I/O request.

22. The method as recited in claim 21, wherein the one or more physical storage devices include a first physical storage device and a second physical storage device, and wherein performing the function includes:

detecting that the I/O request requires access to the first physical storage device and the second physical storage device; and

partitioning the I/O request into a first physical I/O request targeted at the first physical storage device and a second physical I/O request targeted at the second physical storage device.

23. The method as recited in claim 21, wherein the control data includes network path information.

24. The method as recited in claim 23, wherein performing the function includes selecting a first preferred network path to access a first physical storage device of the one or more physical storage devices.

25. The method as recited in claim 24, further comprising:

selecting a second preferred network path to access the first physical storage device upon a detection of a triggering condition.

26. The method as recited in claim 25, wherein the triggering condition is a load imbalance detected in accordance with a load balancing policy.

27. The method as recited in claim 25, wherein the triggering condition is a path failure.

28. A computer accessible medium comprising program instructions, wherein the instructions are executable to:

aggregate storage within one or more physical storage devices into a virtual storage device at an off-host virtualizer;

provide control data for the virtual storage device to a host;

perform a function dependent on the control data at the host in response to an I/O request targeted at the virtual storage device; and

use a result of the function to coordinate one or more I/O operations corresponding to the I/O request.

29. The computer accessible medium as recited in claim 28, wherein the one or more physical storage devices include a first and a second physical storage device, and wherein the function includes:

a detection that the I/O request requires access to the first physical storage device and the second physical storage device; and

a partition of the I/O request into a first physical I/O request targeted at the first physical storage device and a second physical I/O request targeted at the second physical storage device.

30. The computer accessible medium as recited in claim 28, wherein the control data includes network path information.

31. The computer accessible medium as recited in claim 30, wherein the function includes a selection of a first preferred network path to access a first physical storage device of the one or more physical storage devices.

32. The computer accessible medium as recited in claim 31, wherein the instructions are further executable to:

select a second preferred network path to access the first physical storage device upon a detection of a triggering condition.