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Posted to issues@trafficserver.apache.org by "John Plevyak (JIRA)" <ji...@apache.org> on 2010/09/10 00:34:33 UTC
[jira] Created: (TS-436) Documenttation for variable hardware
sector size support
Documenttation for variable hardware sector size support
--------------------------------------------------------
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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[jira] Commented: (TS-436) Documenttation for variable hardware
sector size support
Posted by "John Plevyak (JIRA)" <ji...@apache.org>.
[ https://issues.apache.org/jira/browse/TS-436?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12909320#action_12909320 ]
John Plevyak commented on TS-436:
---------------------------------
I have also added code to auto-detect misaligned partitions on Linux so that if
(for example) /sys/block/sda/sda1/alignment_offset is non-zero, ATS will offset
reads/writes to that disk by that alignment. So if you have a misaligned
partition, and *if* linux knows about it, ATS will compensate.
> Documenttation for variable hardware sector size support
> --------------------------------------------------------
>
> 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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