Data mirror invalid timestamped write handling

Patent metadata

Field	Value
Publication number	US-10101941-B2
Application number	US-201615270917-A
Country	US
Kind code	B2
Filing date	Sep 20, 2016
Priority date	Sep 20, 2016
Publication date	Oct 16, 2018
Grant date	Oct 16, 2018

Abstract

For handling data mirror invalid timestamped write activities, an apparatus is disclosed. The apparatus includes a data mirror that mirrors write activities from a first storage device at a first site to a second storage device at a second site. The apparatus includes a time monitor that retrieves a timestamp for each of the mirrored write activities and monitors a reference clock in a storage control session as a comparison to validate the timestamp for each of the mirrored write activities. If the timestamp of a mirrored write activity is outside of a pre-determined parameter range, then the time monitor identifies the mirrored write activity as having a missing timestamp, assigns a next logical timestamp to the mirrored write activity, and prepares the mirrored write activity for inclusion in a consistency group associated with the next logical timestamp.

First claim

What is claimed is:

1. An apparatus, comprising:
a data mirroring module that mirrors write activities from a first storage device at a first site to a second storage device at a second site; and
a time monitoring module that retrieves a timestamp referencing a first time of a first reference clock on the first site for each of the mirrored write activities and monitors a second reference clock of the second storage site in a storage control session as a comparison of the first and second reference clocks to validate that the timestamp for each of the mirrored write activities on the second site corresponds to a respective write activity on the first site,
wherein in response to the timestamp of a mirrored write activity being determined to be outside of a pre-determined time parameter range corresponding to the second reference clock, the time monitoring module:
identifies the mirrored write activity as having a missing timestamp, assigns a next logical timestamp to the mirrored write activity, and
prepares the mirrored write activity for inclusion in a consistency group associated with the next logical timestamp,
wherein the next logical timestamp includes a current clock value corresponding to a previous clock value of a last valid timestamp referencing a second time of the second reference clock within the pre-determined time parameter range incremented one time count.

2. The apparatus of claim 1 , wherein the reference clock comprises a current time of day clock associated with the storage control session.

3. The apparatus of claim 1 , wherein the consistency group includes a record of the mirrored write activities that are sequenced in sequential order based on the timestamp of each mirrored write activity, and wherein the next logical timestamp of the mirrored write activity preserves the sequential order of the mirrored write activities.

4. The apparatus of claim 1 , wherein valid timestamps for the mirrored write activities refer to mirrored write activities having timestamps within the pre-determined time parameter range.

5. The apparatus of claim 1 , wherein invalid timestamps for the mirrored write activities comprises mirrored write activities having timestamps outside the pre-determined time parameter range.

6. The apparatus of claim 1 , wherein the comparison to validate the timestamp for each of the mirrored write activities includes:
in a first check, the time monitoring module comparing the timestamp of each mirrored write activity with the reference clock, and
in a second check, the time monitoring module comparing the timestamp of each mirrored write activity with recent reads of other mirrored write activities from the same storage control session.

7. The apparatus of claim 1 , wherein after preparing the mirrored write activity for inclusion in the consistency group, the data mirroring module continues mirroring write activities without suspension in sequential order based on the timestamp of each mirrored write activity.

8. The apparatus of claim 1 , further comprising:
a data logging module that logs diagnostic information associated with the mirrored write activities having timestamps outside of the pre-determined time parameter range, including the mirrored write activity having the next logical timestamp and the consistency group associated with the next logical timestamp.

9. The apparatus of claim 1 , wherein the apparatus comprises a system data mover that communicates with the first storage device and the second storage device.

10. The apparatus of claim 9 , wherein the system data mover receives data associated with the mirrored write activities from the first storage device at the first site and provides the data associated with the mirrored write activities to a second storage device at a second site.

11. The apparatus of claim 9 , wherein the system data mover records the mirrored write activities in the consistency group in sequence by order based on the timestamp of each mirrored write activity.

12. The apparatus of claim 1 , wherein the first site and the second site are separated by an extended distance, and wherein the data mirror module provides for data replication over the extended distance between the first and second sites for continuity and disaster recovery of data related to the write activities.

13. A system, comprising:
a first storage device at a first site;
a second storage device at a second site that is separated from the first site by an extended distance; and
a data mover that provides for data replication over the extended distance between the first and second storage devices for continuity and disaster recovery of data related to write activities, the data mover including:
a data mirror that mirrors the write activities from the first storage device at the first site to the second storage device at the second site, and
a time monitor that retrieves timestamps referencing first times of a first reference clock on the first site for the mirrored write activities and monitors a second reference clock of the second storage site in a storage control session as a comparison of the first and second reference clocks to validate that the timestamps for the mirrored write activities on the second site correspond to a respective write activity on the first site,
wherein if a timestamp of a mirrored write activity is within a pre-determined time parameter range, then the time monitoring module: classifies the timestamp as a valid timestamp,
wherein if the timestamp of the mirrored write activity is outside of the pre-determined time parameter range, then the time monitoring module:
classifies the timestamp as an invalid timestamp,
identifies the mirrored write activity having the invalid timestamp as having a missing timestamp,
assigns a next logical timestamp to the mirrored write activity, and
prepares the mirrored write activity for inclusion in a consistency group associated with the next logical timestamp, and

wherein the next logical timestamp includes a current clock value corresponding to a previous clock value of a last valid timestamp referencing a second time of the second reference clock within the pre-determined time parameter range incremented one time count.

14. The system of claim 13 , wherein the reference clock comprises a current time of day clock related to the storage control session.

15. The system of claim 13 , wherein the consistency group includes a record of the mirrored write activities that are sequenced in sequential order based on the timestamp of each mirrored write activity, and wherein the next logical timestamp of the mirrored write activity preserves the sequential order of the mirrored write activities.

16. The system of claim 13 , wherein after preparing the mirrored write activity for inclusion in the consistency group, the data mirror continues mirroring write activities without suspension in sequential order based on the timestamp of each mirrored write activity.

17. The system of claim 13 , wherein the data mover further comprises:
a data logger that logs diagnostic information associated with the mirrored write activities having timestamps outside of the pre-determined time parameter range, including the mirrored write activity having the next logical timestamp and the consistency group associated with the next logical timestamp.

18. A method, comprising:
mirroring write activities received from a first storage device at a first site to a second storage device at a second site;
retrieving a timestamp referencing a first time of a first reference c

Assignees

• IBM

Inventors

• Miller Dash D
• Perez Miguel A
• Reed David C

Classifications

• G06F3/067

  Distributed or networked storage systems, e.g. storage area networks [SAN], network attached storage [NAS] · CPC title

• G06F3/0619 Primary

  in relation to data integrity, e.g. data losses, bit errors · CPC title

• G06F3/0653

  Monitoring storage devices or systems · CPC title

• G06F11/1679

  at clock signal level · CPC title

• G06F2201/835

  Timestamp · CPC title