Method and apparatus for detecting and remedying excessive loop initialization
A drive shelf includes an embedded switching hub (ESH) that monitors Fibre Channel Arbitrated Loop (FC-AL) traffic, including loop initialization requests (LIRs), coming from drives attached to the ESH. When a number of LIRs issued by a single drive within a certain amount of time exceeds a threshold, the drive is bypassed. One threshold (a “burst” threshold) measures the number of LIRs issued within a short period of time. If the number exceeds a threshold that would prevent other data from circulating through the loop, the drive is bypassed. A second threshold (a long-term threshold) measures the number of LIRs issued within a longer period of time. If the drive issues a number of LIRs at a slower rate than the burst threshold, but still above the long-term threshold, the drive is bypassed.
1. A method for monitoring storage devices in a loop comprising:
determining a short-term threshold counting a number of loop initialization requests issued per a first period of time;
determining a long-term threshold counting a number of loop initialization requests issued per a second period of time longer than the first period of time;
monitoring a number of loop initialization requests issued by a storage device coupled to the loop;
determining whether the number of loop initialization requests issued by the storage device exceeds the short-term threshold or the long-term threshold; and
if the number of loop initialization requests issued by the storage device exceeds the short-term threshold or the long-term threshold, functionally removing the storage device from the loop.
2. The method of claim 1 , further comprising:
adjusting the threshold based on a desired data throughput of the loop.
3. The method of claim 1 , wherein bypassing the storage device comprises:
disabling a port coupling the storage device to the loop.
4. The method of claim 3 , wherein monitoring a number of loop initialization requests comprises:
using an embedded switching hub (ESH) including the port coupled to the storage device to count a number of loop initialization requests issued by the storage device.
5. The method of claim 4 , further comprising:
controlling the ESH through an application program interface (API) to perform the monitoring and the removing.
6. The method of claim 1 , further comprising:
fulfilling data requests to the storage device using a redundant storage device.
7. The method of claim 1 , wherein the loop is a FC-AL loop.
8. A system comprising:
a processor;
a memory coupled to the processor, the memory including instructions which, when executed by the processor, cause the system to:
determine a short-term threshold counting a number of loop initialization requests issued per a first period of time;
determine a long-term threshold counting a number of loop initialization requests issued per a second period of time longer than the first period of time;
monitor a number of loop initialization requests issued by a storage device coupled to a loop during a specified period of time;
determine whether the number of loop initialization requests issued by the storage device during the specified period of time exceeds the short-term threshold or the long-term threshold; and
functionally remove the storage device from the loop if the number of loop initialization requests issued by the storage device during the specified period of time exceeds the short-term threshold or the long-term threshold.
9. The system of claim 8 , wherein the processor further is to adjust the threshold based on a desired data throughput of the loop.
10. The system of claim 8 , wherein the processor comprises:
an embedded switching hub (ESH) including a port coupled to the storage device; and
a central processing unit (CPU) coupled to the ESH to control the ESH.
11. The system of claim 10 , wherein the ESH further is to:
report a number of loop initialization requests issued by the storage device; and
disable the port if the number of loop initialization requests exceeds the threshold.
12. The system of claim 10 , wherein the ESH includes an application program interface (API), and wherein the CPU controls the ESH through the API.
13. The system of claim 10 , wherein the loop is an FC-AL loop.
14. A method for monitoring storage devices in a loop comprising:
determining a short-term threshold for a number of loop initialization requests issued over a first time period;
determining a long-term threshold for a number of loop initialization requests issued over a second time period longer than the first time period;
monitoring a number of loop initialization requests issued by a storage device coupled to the loop;
determining whether the number of loop initialization requests issued by the storage device exceeds either the short-term threshold or the long-term threshold; and
if the number of loop initialization requests issued by the storage device exceeds either the short-term threshold or the long-term threshold, bypassing the storage device in the loop.
15. The method of claim 14 , further comprising:
adjusting the short-term threshold and the long-term threshold based on a desired data throughput of the loop.
16. The method of claim 14 :
wherein monitoring the number of loop initialization requests issued by the storage device is performed by an ESH; and
wherein bypassing the storage device in the loop is performed by the ESH.
17. The method of claim 16 , wherein bypassing the storage device in the loop comprises:
disabling a port of the ESH coupled to the storage device.
18. The method of claim 16 , wherein the loop is a FC-Al loop.