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From Elliott Sims <elli...@backblaze.com>
Subject Re: Snapshot SSTable modified??
Date Sat, 26 May 2018 00:05:22 GMT
I've run across this problem before - it seems like GNU tar interprets
changes in the link count as changes to the file, so if the file gets
compacted mid-backup it freaks out even if the file contents are
unchanged.  I worked around it by just using bsdtar instead.

On Thu, May 24, 2018 at 6:08 AM, Nitan Kainth <nitankainth@gmail.com> wrote:

> Jeff,
>
> Shouldn't Snapshot get consistent state of sstables? -tmp file shouldn't
> impact backup operation right?
>
>
> Regards,
> Nitan K.
> Cassandra and Oracle Architect/SME
> Datastax Certified Cassandra expert
> Oracle 10g Certified
>
> On Wed, May 23, 2018 at 6:26 PM, Jeff Jirsa <jjirsa@gmail.com> wrote:
>
>> In versions before 3.0, sstables were written with a -tmp filename and
>> copied/moved to the final filename when complete. This changes in 3.0 - we
>> write into the file with the final name, and have a journal/log to let uss
>> know when it's done/final/live.
>>
>> Therefore, you can no longer just watch for a -Data.db file to be created
>> and uploaded - you have to watch the log to make sure it's not being
>> written.
>>
>>
>> On Wed, May 23, 2018 at 2:18 PM, Max C. <mc_cassandra@core43.com> wrote:
>>
>>> Hi Everyone,
>>>
>>> We’ve noticed a few times in the last few weeks that when we’re doing
>>> backups, tar has complained with messages like this:
>>>
>>> tar: /var/lib/cassandra/data/mars/test_instances_by_test_id-6a944
>>> 0a04cc111e8878675f1041d7e1c/snapshots/backup_20180523_024502/mb-63-big-Data.db:
>>> file changed as we read it
>>>
>>> Any idea what might be causing this?
>>>
>>> We’re running Cassandra 3.0.8 on RHEL 7.  Here’s rough pseudocode of our
>>> backup process:
>>>
>>> <cronjob set to fire same script at same time on all nodes>
>>> SNAPSHOT_NAME=backup_YYYMMDD_HHMMSS
>>> nodetool snapshot -t $SNAPSHOT_NAME
>>>
>>> for each keyspace
>>> - dump schema to “schema.cql"
>>> - tar -czf /file_server/backup_$HOSTNAME_$KEYSPACE_YYYYMMDD_HHMMSS.tgz
>>> schema.cql /var/lib/cassandra/data/$KEYSPACE/*/snapshots/$SNAPSHOT_NAME
>>>
>>> nodetool clearsnapshot -t $SNAPSHOT_NAME
>>>
>>> Thanks.
>>>
>>> - Max
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>>>
>>
>

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