chrishiestand's questions

I have two clusters. Cluster A (on google container engine) is a public facing cluster and it needs to connect to a private Cluster B (a click-to-deploy cluster on GCE) to access a service. I would like to have Cluster A connect to Cluster B through a load balancer, and that can work even though it seems as though all GCE load balancers require a public IP address https://groups.google.com/d/topic/gce-discussion/Dv6289i4_rg/discussion (I'd prefer if it were all private).

The public IP address isn't so bad by itself if you could just set a simple firewall rule and use the standard Google Load Balancer. Unfortunately source-tags don't seem to cross the WAN threshold (or are just not passed by the load balancer). This is the rule that I'd want to use:

gcloud compute firewall-rules create servicename-lb-from-gke-cluster --allow tcp:1234 --source-tags k8s-gke-cluster-node --target-tags servicename #DOES NOT WORK

After entering the above command, Cluster A cannot communicate to Cluster B (via load balancer) through tcp port 1234.

This does work, but it is painful because it requires supervision to automate setting the public IP addresses of the source cluster:

gcloud compute firewall-rules create servicename-lb-from-gke-cluster --allow tcp:1234 --source-ranges 100.2.3.4/32 100.3.5.9/32 100.9.1.2/32 --target-tags servicename #Does work, but is painful

As suggested in the google groups thread, HA proxy is another suggestion.

Another idea is to open up the firewall to the entire WAN and add secure authentication between cluster A and B. Maybe this is a good idea to do for security reasons anyway? The difficulty may range from easy to hard depending on what cluster A and B are running though - it might be nice to have a more general solution.

Does anyone have a better idea? Does anyone else have the same problem?

I am trying to accomplish something that is easy in bash: look for files in a folder and source them if they exist (and do not output if no files exist).

In bourne shells this is how to do it:

  if [ -d /etc/profile.d ]; then
      for f in `ls -1 /etc/profile.d/*.sh 2> /dev/null`; do
          . $f
      done
  fi

I am new to zsh and cannot get the equivalent working. What am I doing wrong?

if [[ -d "/etc/zsh.d" ]]; then
    for file in (ls -1 /etc/zsh.d/*.zsh 2> /dev/null); do
        source $file
    done
fi

fail: parse error near '>'.

I have tried many variations and cannot get it to be as smooth as the sh/bash equivalent. It's as if redirection does not always work within subshells.

On a system I'm running Ubuntu 10.04. My raid-1 restore started out fast but quickly became ridiculously slow (at this rate the restore will take 150 days!):

dimmer@paimon:~$ cat /proc/mdstat 
Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10] 
md0 : active raid1 sdc1[2] sdb1[1]
      1953513408 blocks [2/1] [_U]
      [====>................]  recovery = 24.4% (477497344/1953513408) finish=217368.0min speed=113K/sec

unused devices: <none>

Eventhough I have set the kernel variables to reasonably quick values:

dimmer@paimon:~$ cat /proc/sys/dev/raid/speed_limit_min
1000000

dimmer@paimon:~$ cat /proc/sys/dev/raid/speed_limit_max
100000000

I am using 2 2.0TB Western Digital Hard Disks, WDC WD20EARS-00M and WDC WD20EARS-00J. I believe they have been partitioned such that their sectors are aligned.

dimmer@paimon:/sys$ sudo parted /dev/sdb
GNU Parted 2.2
Using /dev/sdb
Welcome to GNU Parted! Type 'help' to view a list of commands.

(parted) p                                                                
Model: ATA WDC WD20EARS-00M (scsi)
Disk /dev/sdb: 2000GB
Sector size (logical/physical): 512B/512B
Partition Table: gpt

Number  Start   End     Size    File system  Name  Flags
 1      1049kB  2000GB  2000GB  ext4

(parted) unit s

(parted) p                                                                

Number  Start  End          Size         File system  Name  Flags
 1      2048s  3907028991s  3907026944s  ext4

(parted) q                                                                
dimmer@paimon:/sys$ sudo parted /dev/sdc
GNU Parted 2.2
Using /dev/sdc
Welcome to GNU Parted! Type 'help' to view a list of commands.
(parted) p                                                                
Model: ATA WDC WD20EARS-00J (scsi)
Disk /dev/sdc: 2000GB
Sector size (logical/physical): 512B/4096B
Partition Table: gpt

Number  Start   End     Size    File system  Name  Flags
 1      1049kB  2000GB  2000GB  ext4

I am beginning to think that I have a hardware problem, otherwise I can't imagine why the mdadm restore should be so slow.

I have done a benchmark on /dev/sdc using Ubuntu's disk utility GUI app, and the results looked normal so I know that sdc has the capability to write faster than this. I also had the same problem on a similar WD drive that I RMAd because of bad sectors. I suppose it's possible they sent me a replacement with bad sectors too, although there are no SMART values showing them yet.

Any ideas? Thanks.

As requested, output of top sorted by cpu usage (notice there is ~0 cpu usage). iowait is also zero which seems strange:

top - 11:35:13 up 2 days,  9:40,  3 users,  load average: 2.87, 2.58, 2.30
Tasks: 142 total,   1 running, 141 sleeping,   0 stopped,   0 zombie
Cpu(s):  0.0%us,  0.2%sy,  0.0%ni, 99.8%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st
Mem:   3096304k total,  1482164k used,  1614140k free,   617672k buffers
Swap:  1526132k total,        0k used,  1526132k free,   535416k cached

  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND                                                                                  
   45 root      20   0     0    0    0 S    0  0.0   2:17.02 scsi_eh_0                                                                                 
    1 root      20   0  2808 1752 1204 S    0  0.1   0:00.46 init                                                                                      
    2 root      20   0     0    0    0 S    0  0.0   0:00.00 kthreadd                                                                                  
    3 root      RT   0     0    0    0 S    0  0.0   0:00.02 migration/0                                                                               
    4 root      20   0     0    0    0 S    0  0.0   0:00.17 ksoftirqd/0                                                                               
    5 root      RT   0     0    0    0 S    0  0.0   0:00.00 watchdog/0                                                                                
    6 root      RT   0     0    0    0 S    0  0.0   0:00.02 migration/1
  ...                                                               

dmesg errors, definitely looking like hardware:

[202884.000157] ata5.00: exception Emask 0x0 SAct 0x0 SErr 0x0 action 0x6 frozen
[202884.007015] ata5.00: failed command: FLUSH CACHE EXT
[202884.013728] ata5.00: cmd ea/00:00:00:00:00/00:00:00:00:00/a0 tag 0
[202884.013730]          res 40/00:00:ff:59:2e/00:00:35:00:00/e0 Emask 0x4 (timeout)
[202884.033667] ata5.00: status: { DRDY }
[202884.040329] ata5: hard resetting link
[202889.400050] ata5: link is slow to respond, please be patient (ready=0)
[202894.048087] ata5: COMRESET failed (errno=-16)
[202894.054663] ata5: hard resetting link
[202899.412049] ata5: link is slow to respond, please be patient (ready=0)
[202904.060107] ata5: COMRESET failed (errno=-16)
[202904.066646] ata5: hard resetting link
[202905.840056] ata5: SATA link up 3.0 Gbps (SStatus 123 SControl 300)
[202905.849178] ata5.00: configured for UDMA/133
[202905.849188] ata5: EH complete
[203899.000292] ata5.00: exception Emask 0x0 SAct 0x0 SErr 0x0 action 0x6 frozen
[203899.007096] ata5.00: failed command: IDENTIFY DEVICE
[203899.013841] ata5.00: cmd ec/00:01:00:00:00/00:00:00:00:00/00 tag 0 pio 512 in
[203899.013843]          res 40/00:00:ff:f9:f6/00:00:38:00:00/e0 Emask 0x4 (timeout)
[203899.041232] ata5.00: status: { DRDY }
[203899.048133] ata5: hard resetting link
[203899.816134] ata5: SATA link up 3.0 Gbps (SStatus 123 SControl 300)
[203899.826062] ata5.00: configured for UDMA/133
[203899.826079] ata5: EH complete
[204375.000200] ata5.00: exception Emask 0x0 SAct 0x0 SErr 0x0 action 0x6 frozen
[204375.007421] ata5.00: failed command: IDENTIFY DEVICE
[204375.014799] ata5.00: cmd ec/00:01:00:00:00/00:00:00:00:00/00 tag 0 pio 512 in
[204375.014800]          res 40/00:00:ff:0c:0f/00:00:39:00:00/e0 Emask 0x4 (timeout)
[204375.044374] ata5.00: status: { DRDY }
[204375.051842] ata5: hard resetting link
[204380.408049] ata5: link is slow to respond, please be patient (ready=0)
[204384.440076] ata5: SATA link up 3.0 Gbps (SStatus 123 SControl 300)
[204384.449938] ata5.00: configured for UDMA/133
[204384.449955] ata5: EH complete
[204395.988135] ata5.00: exception Emask 0x0 SAct 0x0 SErr 0x0 action 0x6 frozen
[204395.988140] ata5.00: failed command: IDENTIFY DEVICE
[204395.988147] ata5.00: cmd ec/00:01:00:00:00/00:00:00:00:00/00 tag 0 pio 512 in
[204395.988149]          res 40/00:00:ff:0c:0f/00:00:39:00:00/e0 Emask 0x4 (timeout)
[204395.988151] ata5.00: status: { DRDY }
[204395.988156] ata5: hard resetting link
[204399.320075] ata5: SATA link up 3.0 Gbps (SStatus 123 SControl 300)
[204399.330487] ata5.00: configured for UDMA/133
[204399.330503] ata5: EH complete

We're upgrading several systems from Debian Lenny to Squeeze and I'd like to ensure that I haven't missed any grub2 installations. By default, Squeeze chain-boot-loads from grub1 and you have to run upgrade-from-grub-legacy to upgrade. So I'd like to be able to remotely check to see if grub2 has been installed in the disk boot sector without rebooting, and without overwriting the boot sector.

Is there anything easier than doing a hexdump of the early blocks of the hard drive and trying to identify grub2-specific bytes?

I have a 6 disk raid6 mdadm array I'd like to benchmark writes to:

root@ubuntu:~# cat /proc/mdstat 
Personalities : [raid6] [raid5] [raid4] 
md0 : active raid6 sda[0] sdf[5] sde[4] sdd[3] sdc[2] sdb[1]
      1953545984 blocks level 6, 64k chunk, algorithm 2 [6/6] [UUUUUU]

Benchmarks can be inaccurate because of cache - for example, notice the write speed here is higher than it should be:

root@ubuntu:/mnt/raid6# dd if=/dev/zero of=delme bs=1M count=100
100+0 records in
100+0 records out
104857600 bytes (105 MB) copied, 0.276026 s, 380 MB/s

Now we can disable each disk cache pretty easily:

root@ubuntu:~# hdparm -W0 /dev/sd*

/dev/sda:
 setting drive write-caching to 0 (off)
 write-caching =  0 (off)

/dev/sdb:
 setting drive write-caching to 0 (off)
 write-caching =  0 (off)

/dev/sdc:
 setting drive write-caching to 0 (off)
 write-caching =  0 (off)

/dev/sdd:
 setting drive write-caching to 0 (off)
 write-caching =  0 (off)

/dev/sde:
 setting drive write-caching to 0 (off)
 write-caching =  0 (off)

/dev/sdf:
 setting drive write-caching to 0 (off)
 write-caching =  0 (off)

But there is still Linux caching:

root@ubuntu:/mnt/raid6# dd if=/dev/zero of=delme bs=1M count=10
10+0 records in
10+0 records out
10485760 bytes (10 MB) copied, 0.00566339 s, 1.9 GB/s

To disable Linux caching, we can mount the filesystem synchronously:

mount -o remount,sync /mnt/raid6

But after this writes become way slower than they should be:

root@ubuntu:/mnt/raid6# dd if=/dev/zero of=delme bs=1M count=10
10+0 records in
10+0 records out
10485760 bytes (10 MB) copied, 23.3311 s, 449 kB/s

It's as if mdadm requires async mounts in order to function. What's going on here?