1. A computer system comprising:
a storage system; and
a management system coupled to the storage system via a network and configured to manage the storage system,
wherein the storage system includes a plurality of pools each of which includes a plurality of storage resources and is separated into a plurality of tiers different in access performance;
wherein the management system monitors access performance of the plurality of pools to detect a risky pool which is expected to become unable to satisfy predetermined access performance requirements;
wherein the management system estimates access performance of each of one or more candidate pools in the plurality of pools in a case where a storage resource thereof migrates to the risky pool, by simulation based on variations in data arrangement in the pool caused by evacuating data held in the storage resource in the same pool for the migration of the storage resource; and
wherein the management system determines that the storage resource migrates from a source pool of which the estimated access performance satisfies predetermined performance requirements to the risky pool.
2. A computer system according to claim 1, wherein the management system estimates the access performance of each of the one or more candidate pools during a period of the data evacuation using a predicted data arrangement varied by data relocation for the storage resource to migrate and estimated additional load caused by the data relocation for the storage resource to migrate.
3. A computer system according to claim 2,
wherein, in the estimation of the time variation of the access performance by simulation, the management system estimates the access performance of each of the one or more candidate pools in a period in which data relocation does not occur in the candidate pool using predicted data arrangement in the candidate pool; and
wherein, in the estimation of the time variation of the access performance by simulation, the management system estimates the access performance of each of the one or more candidate pools in a period in which data relocation occurs in the candidate pool using estimated additional load caused by the data relocation in the candidate pool in addition to predicted data arrangement in the candidate pool.
4. A computer system according to claim 3, wherein the management system repeats the estimation of the access performance of each of the one or more candidate pools while advancing the start time of the data evacuation to find a start time of data evacuation with which the estimated access performance satisfies the predetermined performance requirements of the candidate pool.
5. A computer system according to claim 4, wherein the management system selects a candidate pool in which an expected completion time of the data evacuation is the earliest as the source pool from the one or more candidate pools in which the estimated access performance satisfies the predetermined performance requirements.
6. A computer system according to claim 5,
wherein the management system holds history information on accesses to each of the one or more candidate pools collected from the storage system and information on access performance of individual tiers in each of the one or more candidate pools; and
wherein the management system estimates the access performance of each of the one or more candidate pools using the access history information and the information on access performance in periods during the data evacuation and after the completion of the data evacuation.
7. A computer system according to claim 6, wherein, in a case where the simulation includes an inter-tier rearrangement after the completion of evacuating the data in the storage resource, the management system estimates access performance of each of the one or more candidate pools during the inter-tier rearrangement after the completion of the data evacuation using predicted data arrangement changed by a tier-to-tier data relocation in the candidate pool and estimated additional load caused by the tier-to-tier data relocation.
8. A computer system according to claim 7, wherein the management system estimates access performance of each of the one or more candidate pools in both of a case where the inter-tier rearrangement is carried out immediately after evacuating the data in the storage resource and a case where the inter-tier rearrangement is not carried out immediately after evacuating the data in the storage resource.
9. A computer system according to claim 8,
wherein the management system monitors accesses to the source pool while the storage resource is migrating from the source pool to the risky pool; and
wherein the management system determines whether to abort the migration of the resource based on the monitored accesses to the source pool and the estimated access performance of the source pool.
10. A method of managing a storage system in a computer system, the computer system including the storage system which includes a plurality of storage resources and a plurality of pools separated into a plurality of tiers different in access performance and a management system connected to the storage system via a network to manage the storage system, the method comprising:
monitoring, by the management system, access performance of the plurality of pools to detect a risky pool which is expected to become unable to satisfy predetermined access performance requirements;
estimating, by the management system, access performance of each of one or more candidate pools in the plurality of pools in a case where a storage resource migrates to the risky pool, by simulation based on variations in data arrangement in the candidate pool caused by evacuating data held in the storage resource in the same pool for the migration of the storage resource; and
determining, by the management system, that the storage resource migrates from a source pool of which the estimated access performance satisfies predetermined performance requirements to the risky pool.
11. A method of managing a storage system according to claim 10, further comprising:
estimating, by the management system, the access performance of each of the one or more candidate pools during a period of the data evacuation using predicted data arrangement varied by data relocation for the storage resource to migrate and estimated additional load caused by the data relocation for the storage resource to migrate.
12. A method of managing a storage system according to claim 10, further comprising:
repeating, by the management system, the estimating the access performance of each of the one or more candidate pools while advancing the start time of the data evacuation to find a start time of data evacuation with which the estimated access performance satisfies the predetermined performance requirements; and
selecting, by the management system, a candidate pool in which an expected completion time of the data evacuation is the earliest as the source pool from the one or more candidate pools in which the estimated access performance satisfies the predetermined performance requirements.
13. A method of managing a storage system according to claim 10, further comprising:
storing, by the management system, history information on accesses to each of the one or more candidate pools collected from the storage system and information on access performance of individual tiers in each of the one or more candidate pools; and
estimating, by the management system, access performance of each of the one or more candidate pools using the access history information and the information on access performance in periods during the data evacuation and after the completion of the data evacuation.
14. A method of managing a storage system according to claim 10, further comprising:
estimating, by the management system, the access performance of each of the one or more candidate pools during an inter-tier rearrangement after the completion of the data evacuation using predicted data arrangement changed by a tier-to-tier data relocation in the candidate pool and estimated additional load caused by the tier-to-tier data relocation in a case where the simulation includes the inter-tier rearrangement after the completion of evacuating the data in the storage resource.
15. A method of managing a storage system according to claim 14, further comprising:
estimating, by the management system, access performance of each of the one or more candidate pools in both of a case where the inter-tier rearrangement is carried out immediately after evacuating the data in the storage resource and a case where the inter-tier rearrangement is not carried out immediately after evacuating the data in the storage resource.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A ball training apparatus comprising:
an elastic cord; and
a fastener capable of being at least partially received between a bladder and a sheath of an inflatable ball, the fastener being configured to permit an end of the elastic cord to be attached to the fastener, the elastic cord being configured so that, when the ball is struck, the ball is capable of sufficient travel for a user to observe the flight of the ball and of returning to a position in which retrieval of the ball is facilitated.
2. The ball training apparatus as claimed in claim 1, in which the fastener includes a stop that is elongated and hinged to define two portions that are capable of pivoting towards each other to reduce a plan profile of the stop to facilitate insertion of the stop through an opening in the sheath so that subsequent pivoting away from each other serves to resist extraction of the stop from the opening.
3. The ball training apparatus as claimed in claim 2, in which the fastener includes a connector attached to the stop at a position about halfway along the length of the stop and between said portions, the connector extending through the opening in the sheath for connection to the cord.
4. The ball training apparatus as claimed in claim 3, in which the connector is a swivel connector so that twisting of the cord and subsequent entanglement resulting from rotation of the ball relative to the cord is reduced.
5. The ball training apparatus as claimed in claim 4, in which the swivel connector includes a pivot pin that extends from the stop, a looped connector being mounted on the pivot pin and rotatable with respect to the pivot pin.
6. The ball training apparatus as claimed in claim 2, in which the stop is configured so that, when the bladder is inflated, the portions of the stop are driven apart further to secure the stop between the bladder and the sheath.
7. The ball training apparatus as claimed in claim 1, which includes an anchor for use on a support surface, the anchor being formed from a material affording the anchor a weight and surface property so as to resist displacement of the anchor relative to the support surface within a stretching threshold of the elastic chord.
8. The ball training apparatus as claimed in claim 7, which includes an anchoring accessory for anchoring the anchor to a substrate.
9. The ball training apparatus as claimed in claim 8, in which the anchoring accessory is in the form of an auger tool having a handle and a stem extending from the handle, a free end of the stem being sharpened so that the stem is able to be inserted into the substrate, an auger formation being arranged on the stem so that the stem can be screwed into the substrate.
10. The ball training apparatus as claimed in claim 9, in which the anchor defines an opening through which the stem of the auger can be passed prior to screwing the stem into the substrate.
11. The ball training apparatus as claimed in claim 10, in which the anchor includes a base with an opening through which the end of the cord can be threaded to allow the cord to be tied to the base and a cord-retaining formation to facilitate winding of the cord onto the base.
12. The ball training apparatus as claimed in claim 11, in which the base defines a kicking ball support formation so that the ball can be supported in a kicking position on the base.
13. The ball training apparatus as claimed in claim 12, which includes a strike ball support that is mountable on the base for supporting a ball at a suitable height for striking.
14. A ball training apparatus comprising:
an inflatable ball having an inflatable bladder located within a sheath;
an elastic cord; and
a fastener at least partially received between the bladder and the sheath, an end of the elastic cord attached to the fastener, the elastic cord being configured so that, when the ball is struck, the ball is capable of sufficient travel for a user to observe the flight of the ball and of returning to a position in which retrieval of the ball is facilitated.
15. A method of fastening an elastic cord to an inflatable ball having an inflatable bladder located with a sheath, the method comprising:
forming an opening in the sheath;
inserting a fastener at least partially through the opening;
attaching the elastic cord to the fastener; and
inflating the bladder.