When my server is downloading a file or executing other IO operations the other server functions become extremely slow (almost locked). Even other functions that do not use the network. When a download is in progress, if I start typing in gnome-terminal, the first key I type delay several seconds to appear on the screen and much times it is repeated several times the letter, even typing only once.
Seconds before I start a download I execute a sar command:
[root@hostname ~]# sar 6 36
Linux 2.6.18-348.6.1.el5 (hostname) 07-07-2013
13:16:42 CPU %user %nice %system %iowait %steal %idle
13:16:48 all 3,96 0,00 6,50 4,94 0,00 84,59
13:16:54 all 8,33 0,00 0,88 1,35 0,00 89,44
13:17:00 all 4,81 0,00 1,17 0,17 0,00 93,85
13:17:06 all 2,49 0,00 2,44 0,80 0,00 94,27
13:17:12 all 6,42 0,00 10,02 24,08 0,00 59,48
13:17:18 all 1,61 0,00 17,16 28,87 0,00 52,36
13:17:24 all 6,46 0,00 14,03 10,66 0,00 68,86
13:17:30 all 10,66 0,00 16,76 4,93 0,00 67,65
13:17:36 all 8,41 0,00 21,28 19,07 0,00 51,25
13:17:42 all 4,98 0,00 18,10 47,51 0,00 29,41
13:17:48 all 0,48 0,00 13,87 28,22 0,00 57,44
13:17:54 all 0,53 0,00 13,80 42,60 0,00 43,08
13:18:00 all 1,08 0,00 12,62 57,36 0,00 28,94
13:18:06 all 1,90 0,00 15,37 63,71 0,00 19,02
13:18:12 all 1,10 0,00 16,26 71,44 0,00 11,21
13:18:18 all 1,65 0,00 21,12 72,99 0,00 4,25
13:18:24 all 1,38 0,00 22,54 67,81 0,00 8,27
13:18:30 all 1,25 0,00 17,00 67,94 0,00 13,81
13:18:36 all 1,33 0,00 16,87 51,04 0,00 30,76
13:18:42 all 1,27 0,00 17,91 58,54 0,00 22,28
13:18:48 all 1,39 0,00 14,60 39,19 0,00 44,82
13:18:54 all 1,78 0,00 13,68 35,70 0,00 48,85
13:19:00 all 0,43 0,00 10,63 54,44 0,00 34,50
13:19:06 all 6,58 0,00 8,81 13,92 0,00 70,69
13:19:12 all 0,89 0,00 27,40 19,09 0,00 52,63
13:19:18 all 1,63 0,00 20,10 39,95 0,00 38,32
13:19:24 all 18,95 0,00 16,89 34,02 0,00 30,15
13:19:30 all 4,21 0,00 9,03 17,51 0,00 69,24
13:19:36 all 0,87 0,00 3,40 2,13 0,00 93,60
13:19:42 all 2,17 0,00 0,46 0,13 0,00 97,25
13:19:48 all 2,90 0,00 1,53 2,17 0,00 93,40
13:19:54 all 2,17 0,00 11,44 17,07 0,00 69,31
13:20:00 all 1,10 0,00 1,86 0,04 0,00 97,00
13:20:06 all 1,71 0,00 0,63 0,38 0,00 97,28
13:20:12 all 1,93 0,00 1,30 0,42 0,00 96,36
13:20:18 all 0,12 0,00 0,38 0,04 0,00 99,46
Média: all 3,32 0,00 10,74 24,91 0,00 61,03
No erros appear in /var/log/messages.
My disks are two SSD Kingston SH103S3240G in RAID-1 partitioned as follows:
[root@cluster ~]# fdisk -l
Disk /dev/hda: 240.0 GB, 240057409536 bytes
255 heads, 63 sectors/track, 29185 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/hda1 1 14 112423+ fd Linux raid autodetect
/dev/hda2 15 537 4200997+ fd Linux raid autodetect
/dev/hda3 538 29185 230115060 fd Linux raid autodetect
Disk /dev/hdc: 240.0 GB, 240057409536 bytes
255 heads, 63 sectors/track, 29185 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/hdc1 1 14 112423+ fd Linux raid autodetect
/dev/hdc2 15 537 4200997+ fd Linux raid autodetect
/dev/hdc3 538 29185 230115060 fd Linux raid autodetect
Disk /dev/md125: 235.6 GB, 235637702656 bytes
2 heads, 4 sectors/track, 57528736 cylinders
Units = cylinders of 8 * 512 = 4096 bytes
Disk /dev/md125 doesn't contain a valid partition table
Disk /dev/md1: 4301 MB, 4301717504 bytes
2 heads, 4 sectors/track, 1050224 cylinders
Units = cylinders of 8 * 512 = 4096 bytes
Disk /dev/md1 doesn't contain a valid partition table
Disk /dev/md127: 115 MB, 115015680 bytes
2 heads, 4 sectors/track, 28080 cylinders
Units = cylinders of 8 * 512 = 4096 bytes
Disk /dev/md127 doesn't contain a valid partition table
My question is: How can I diagnose this problem if it occurs when the computer is extremely slow to type commands and see the output?
The server is so slow that you can not analyze the output of the commands iotop and top.
