[LUDOC-144] Watching the OST Block I/O Stream (Ch 31)

• Status: Resolved
• Project: Lustre Documentation
• Type: Bug
• Priority: Minor
• Reporter: Brett Lee (Inactive)
• Assignee: Linda Bebernes (Inactive)
• Resolution: Fixed
• Labels: QContent
• Business Value: 4.25
• Severity: 3

Description

In section 31.2.6. Watching the OST Block I/O Stream

a. The table is misaligned
b. Some row headings read differently than in Lustre 1.8.9 (version specific?)
discont pages vs. discontiguous pages (same with blocks)
c. Should have some live data in the table instead of all "0's"
d. Descriptions of discontiguous pages and blocks should be more descriptive, and ideally indicate what may be causing those numbers.
e. Some row headings do not have descriptions. Should also follow "d" above.

Comments

[Brett Lee (Inactive)]

Clarification from Andreas on the meaning of discontiguous pages and blocks:

The distinction is that in brw_stats "pages" refer to what the client submitted in the RPC, while "blocks" refer to what the OST submitted to disk. If there are discontiguous pages it means random or small IO submitted by the client. Discontiguous blocks relate to on-disk fragmentation.

[Brett Lee (Inactive)]

1. brw_stats - "discontiguous pages" refers to data from a client in an RPC that is not in contiguous pages, indicating small or random IO.
2. brw_stats - "discontiguous blocks" refers to an IO operation that did not write sequential blocks of data, such as would be seen with small or random IO.
3. brw_stats - "disk fragmented I/Os" refers to writing to fragmented files, indicating there are not sufficient sequential blocks available on target.

[Linda Bebernes (Inactive)]

Changes are ready for review at http://review.whamcloud.com/#/c/6941/

[Linda Bebernes (Inactive)]

Change merged 7/16