FAQ
Hi All,

I am using TTL 3 hours and GC grace 0 for a CF. I have a normal CF that has
records with TTL 3 hours and I dont send any delete request. I just wonder
if using GC grace 0 will cause any problem except extra Memory/IO/network
load. I know that gc grace is for not transferring deleted records after a
down node comes back. So I assumed that transferring expired records will
not cause any problem.

Do you have any idea? Thank you!

Regards,
Cem.

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  • Peter Schuller at Mar 11, 2012 at 10:03 pm

    I am using TTL 3 hours and GC grace 0 for a CF. I have a normal CF that has
    records with TTL 3 hours and I dont send any delete request. I just wonder
    if using GC grace 0 will cause any problem except extra Memory/IO/network
    load. I know that gc grace is for not transferring deleted records after a
    down node comes back. So  I assumed that transferring expired records will
    not cause any problem.

    Do you have any idea? Thank you!
    If you do not perform any deletes at all, a GC grace of 0 should be
    fine. But if you don't, the GC grace should not really be relevant
    either. So I suggest leaving GC grace high in case you do start doing
    deletes.

    Columns with TTL:s will disappear regardless of GC grace.

    If you do decide to run with short GC grace, be aware of the
    consequencues: http://wiki.apache.org/cassandra/Operations#Dealing_with_the_consequences_of_nodetool_repair_not_running_within_GCGraceSeconds

    --
    / Peter Schuller (@scode, http://worldmodscode.wordpress.com)
  • Cem at Mar 12, 2012 at 9:03 am
    Thank you for the swift response.

    Cem.
    On Sun, Mar 11, 2012 at 11:03 PM, Peter Schuller wrote:

    I am using TTL 3 hours and GC grace 0 for a CF. I have a normal CF that has
    records with TTL 3 hours and I dont send any delete request. I just wonder
    if using GC grace 0 will cause any problem except extra Memory/IO/network
    load. I know that gc grace is for not transferring deleted records after a
    down node comes back. So I assumed that transferring expired records will
    not cause any problem.

    Do you have any idea? Thank you!
    If you do not perform any deletes at all, a GC grace of 0 should be
    fine. But if you don't, the GC grace should not really be relevant
    either. So I suggest leaving GC grace high in case you do start doing
    deletes.

    Columns with TTL:s will disappear regardless of GC grace.

    If you do decide to run with short GC grace, be aware of the
    consequencues:
    http://wiki.apache.org/cassandra/Operations#Dealing_with_the_consequences_of_nodetool_repair_not_running_within_GCGraceSeconds

    --
    / Peter Schuller (@scode, http://worldmodscode.wordpress.com)

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postedMar 11, '12 at 10:37a
activeMar 12, '12 at 9:03a
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