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Re: [Linux-cluster] GFS - Preformance small files



Leonardo D'Angelo Gonçalves wrote:
Hi

I have a GFS cluster on RHEL4.8 which one filesystem (10G) with  various
directories and sub-directories and small files about 5Kb. When I run the
command "du-sh" in the directory it generates about 1500 IOPS on the disks,
for GFS it takes time about 5 minutes and 2 second for ext3 filesyem. Could
someone help me with this problem. follows below the output of gfs_tool
Why for GFS it takes 5 minutes and ext3 2 seconds ? Is there any relation ?
ilimit1 = 100
ilimit1_tries = 3
ilimit1_min = 1
ilimit2 = 500
ilimit2_tries = 10
ilimit2_min = 3
demote_secs = 300
incore_log_blocks = 1024
jindex_refresh_secs = 60
depend_secs = 60
scand_secs = 5
recoverd_secs = 60
logd_secs = 1
quotad_secs = 5
inoded_secs = 15
glock_purge = 0
quota_simul_sync = 64
quota_warn_period = 10
atime_quantum = 3600
quota_quantum = 60
quota_scale = 1.0000   (1, 1)
quota_enforce = 1
quota_account = 1
new_files_jdata = 0
new_files_directio = 0
max_atomic_write = 4194304
max_readahead = 262144
lockdump_size = 131072
stall_secs = 600
complain_secs = 10
reclaim_limit = 5000
entries_per_readdir = 32
prefetch_secs = 10
statfs_slots = 64
max_mhc = 10000
greedy_default = 100
greedy_quantum = 25
greedy_max = 250
rgrp_try_threshold = 100
statfs_fast = 0
seq_readahead = 0



------------------------------------------------------------------------

Leonardo

I'm not sure if 4.8 supports it, but in 5.4, the plock_rate_limit option in cluster.conf has a terrible default which can causes this type of slow down. I have these statements in my <cluster> block in my cluster.conf:

<dlm plock_rate_limit="0"/>
<gfs_controld plock_rate_limit="0" plock_ownership="0"/>

Searching the web, there are a lot of recommendations to set plock_ownership to 1, but its benefit is more workload dependent than plock_rate_limit.

-Andrew


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