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From Karl Hiramoto <>
Subject reducing disk usage advice
Date Sun, 13 Mar 2011 18:10:13 GMT

I'm looking for advice on reducing disk usage.   I've ran out of disk 
space two days in a row while running a  nightly scheduled nodetool 
repair && nodetool compact  cronjob.

I have 6 nodes RF=3  each with 300 GB drives at a hosting company. 
GCGraceSeconds= 260000 (3.1 days)

Every column in the database has a TTL of 86400 (24 hours)   to handle 
deletion of stale data.   50% of the time the data is only written once, 
read 0 or many times then expires. The other 50% of the time it's 
written multiple times, resetting the TTL to 24 hours each time.

One question,  since I use a TTL is it safe to set GCGraceSeconds  to 
0?   I don't manually delete ever, I just rely on the TTL for deletion, 
so are forgotten deletes an issue?

  Read Count: 32052
         Read Latency: 3.1280378135529765 ms.
         Write Count: 9704525
         Write Latency: 0.009527474760485443 ms.
         Pending Tasks: 0
                 Column Family: Offer
                 SSTable count: 12
                 Space used (live): 59865089091
                 Space used (total): 76111577830
                 Memtable Columns Count: 39355
                 Memtable Data Size: 14726313
                 Memtable Switch Count: 414
                 Read Count: 32052
                 Read Latency: 3.128 ms.
                 Write Count: 9704525
                 Write Latency: 0.010 ms.
                 Pending Tasks: 0
                 Key cache capacity: 1000
                 Key cache size: 1000
                 Key cache hit rate: 2.4805931214280473E-4
                 Row cache: disabled
                 Compacted row minimum size: 36
                 Compacted row maximum size: 1597
                 Compacted row mean size: 1319

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