Why does cold start only read some of the disk?


#1

FAQ - Why does cold start only read some of the disk?

Detail

When a node is cold starting and reading records back from disk it gives a percentage complete figure. In some circumstances, such as the example below, the read is marked as successful when only a small percentage of the disk has been scanned. Why is that?

Jul 26 2016 23:43:14 GMT-0400: INFO (namespace): (namespace_ee.c:88) ns *** beginning COLD start
Jul 26 2016 23:43:15 GMT-0400: INFO (drv_ssd): (drv_ssd.c:3173) device /dev/sdb: reading device to load index
Jul 26 2016 23:43:15 GMT-0400: INFO (drv_ssd): (drv_ssd.c:3178) In TID 118773: Using arena #150 for loading data for namespace "***"
Jul 26 2016 23:43:17 GMT-0400: INFO (drv_ssd): (drv_ssd.c:3974) {***} loaded 790764 records, 0 subrecords, /dev/sdb 0%
Jul 26 2016 23:43:19 GMT-0400: INFO (drv_ssd): (drv_ssd.c:3974) {***} loaded 1476460 records, 0 subrecords, /dev/sdb 0%
...
Jul 26 2016 23:57:41 GMT-0400: INFO (drv_ssd): (drv_ssd.c:3974) {***} loaded 134402576 records, 0 subrecords, /dev/sdb 24%
Jul 26 2016 23:57:41 GMT-0400: INFO (drv_ssd): (drv_ssd.c:3199) device /dev/sdb: read complete: UNIQUE 134416496 (REPLACED 10241266) (OLDER 56284290) (EXPIRED 30877634) (MAX-TTL 0) records

Answer

The percentage of the disk given in log messages is the percentage of the total disk. Cold start will only read the portion of disk that actually has data on. When it reaches the end of the data it will mark the read as complete. In the example above, only 24% of the disk contained data, once this was read, no further reading was necessary and the read was marked as complete.

Keywords

COLD START READ DISK PERCENTAGE LOW LESS PARTIAL

Timestamp

8/1/16


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