Documenttation for variable hardware sector size support
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Key: TS-436
URL: https://issues.apache.org/jira/browse/TS-436
Project: Traffic Server
Issue Type: Improvement
Components: Documentation
Affects Versions: 2.2.0
Reporter: John Plevyak
Assignee: Miles Libbey
Fix For: 2.2.0
TS-43
Adds support for auto-detecting drives which have 4096 (well, between 512-8192)
sector size
and using that as the element of atomicity in the cache.
Add (optional/hidden) config:
CONFIG proxy.config.cache.force_sector_size INT
to force a sector size (e.g. 4096) for ALL disks.
SSDs and "advanced format" drives lie about their sector size and
claim 512. The handling of this is still in flux in linuxland hence the option
to force a particular sector size. Note: it is safe to force a higher size
than the hardware supports natively as we still only count on atomicity
in 512 byte increments.
4096 sector size drives formatted for windows will have partitions aligned on
63 512
byte sector boundaries which will mean they will be unaligned.. There are
workarounds, but
you need to do some research on your particular drive. For example, some
drives have a one
time option to switch the partition boundary, others might require reformatting
or repartitioning.
To be safe in Linux you could just use the entire
drive: /dev/sdb instead of /dev/sdb1 and TS will do the right thing.
This feature should work fine when we get out of the difficult transition stage,
in the mean time caveat emptor.
Partitions formatted to support hardware sector
size of more than 512 (e.g. 4096) will result in all objects stored
in the cache to be integral multiples of 4096 bytes which will result in
some waste for small files.
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