How to figure out and solve slow disks?

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Operating Systems Solaris How to figure out and solve slow disks?

06-23-2011

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How to figure out and solve slow disks?

I'm using SUN x4600 with 64GB ram and 2 SAS 146GB 10krpm with Solaris 10

One told me, that the system seems to be slow, so I did a
iostat -xtc 5 2

which showed for a long period of time only 4-6000 kw/s and 100%b

PHP Code:


dbserver:~ #  iostat -xtc 5 200
                 extended device statistics                    tty         cpu
device    r/s    w/s   kr/s   kw/s wait actv  svc_t  %w  %b  tin tout  us sy wt id
sd0       0.0    0.0    0.0    0.0  0.0  0.0    0.0   0   0    0    6   1  1  0 98
sd1       1.2   76.3  154.3 4266.3  1.3  5.4   86.1   1 100 
sd2       1.0    0.9   14.7    2.6  0.0  0.0   14.5   0   1

This looks slow to me, too.
Are there more tools to discover the reason or where might I solve the root cause?

Thanks Stefan

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06-23-2011

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dtrace might be good to find what you're watchin for:

Code:

# Files opened by process,
dtrace -n 'syscall::open*:entry { printf("%s %s",execname,copyinstr(arg0)); }'
 
# Read bytes by process,
dtrace -n 'sysinfo:::readch { @bytes[execname] = sum(arg0); }'
 
# Write bytes by process,
dtrace -n 'sysinfo:::writech { @bytes[execname] = sum(arg0); }'
 
# Read size distribution by process,
dtrace -n 'sysinfo:::readch { @dist[execname] = quantize(arg0); }'
 
# Write size distribution by process,
dtrace -n 'sysinfo:::writech { @dist[execname] = quantize(arg0); }'
 
# Disk size by process,
dtrace -n 'io:::start { printf("%d %s %d",pid,execname,args[0]->b_bcount); }'

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06-23-2011

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iostat vs. dtrace

Thanks DukeNuke2,

sorry for being not precise enough:
I have 2 times 2 SAS 146GB, configured as 2 RAID 1

The Volume I'm talking about is only used by the database (MySQL Cluster) and is mounted as:

Code:

/DB on /dev/dsk/c1t2d0s1 read/write/setuid/devices/intr/largefiles/logging/xattr/noatime/onerror=panic/dev=7c0041 on Thu Jun 23 10:57:32 2011

My problem does not seem to be the number of processes, accessing the files (should only be some of the MySQL ndbmtd process) and also not the number of files (<20) on that drive.

The figures themselves are looking very slow.
I don't think, that this box is only capable for 6 Mbyte /s....

Any Idea?

Last edited by fpmurphy; 06-23-2011 at 10:13 AM.. Reason: code tags, spelling

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06-24-2011

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The disk is doing 80 IO operations per second.

That's not great for a 10K rpm SAS drive, but it's not unreasonable either.

What kind of file system and what are your mount options? (They don't all show up in the output from "mount".)

Last edited by achenle; 06-24-2011 at 03:26 PM..

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