c2h2's questions

I'm going to purchase a 14 bay HP 2U server with ECC memory and bunch of 3TB enterprise SATA drives. I would prefer to make 2 x RAID6 with 6 drive each. This will be used for local office storage and my Internet crawler.

I am flooded with FS/RAID choices. I am wondering should I use Hardware Raid Card, LVM, mdadm, btrfs, fuse zfs? will likely to use debain/ubuntu as OS.

My priority of concerns is:

1. data security, no loss, no corruption (most important)
2. reasonable performance
3. minimal maintenance and easier recovery/replacement if anything goes wrong

Has anyone with production experience?

EDIT: add fuse-zfs

My company has around 20 servers which we want to operate in an underground room, where the temperature over whole year ranges from 5°C to 28°C.

The only thing I am worried about is that in the summertime, the place will be relatively humid, around 80% RH. Will this cause a big impact on the stability of 7x24 running hardware OR shorten the life span of the servers?

In a VOIP application, I have upto 3000 clients rsync audio files from there linux server in a daily, server is placed at a data center (10Mbps in/out bound), the server works as a VOIP sip server running FreeSWITCH (low ping latency should be ensured.)

Therefore I would like to have server side control of rsync which controls:

1. Limit total outbound bandwidth.
2. Limit total number of connections. (Reject clients while at max number of connection and let it retry after a specific time frame.)
3. OPTIONAL: list/kill individual connections.

Normally I would use ssh + rsync + pem_keys with some extra options, but above requirements are not feasible by simple command lines. Can anyone point me some direction. or show some scripts/tools? I would also probably integrate them and release on github. Thanks!

I am using virtualbox 4.1.16 on a Ubuntu 12.04 x64 vm host and all NAT is working properly, like HOST 2222 -> Client 22

But I have changed my HOST sshd to listen on port 81 and restarted, so host port 22 is free. and order my guest vm to do a NAT (HOST)22 to (CLIENT)22. while the same vm guest, if I map NAT 1234 to 22, it works again.

I have tried ufw disable, /etc/init.d/apparmor stop, nothing helps

Is there anything I need to do to make it happen?

I have upgrade my server to a new OS and newer hardware.

But newly installed OS generated a new set of fingerprint / server keys. Is there anyway I could copy it from my old server to new server. In order to remove the security warning from clients?

EDIT: OS change is from ubuntu 11.10 -> 12.04

Is it possible to create a run another custom dhcp service on different UDP port.

For example port 70 and 71?

Therefore all my clients pre-configured to accept this instruction and if fails fall back to official dhcp port?

Suppose you are doing a full speed write to disk in a linux pc box with ssd or mechanical disk (OS also on the same disk, there is no battery/UPS):

cat /dev/urandom > omg.txt

If the power losses suddenly during the process, or any other sort of ungracefully shutdown/reset.

Will the file be corrupted and unable to fix (i.e. none of any data can be recovered?), will there be a chance the file system be completely unable to boot?

Background:

I have some AIO application machines, (running ubuntu with rails + mongodb + chromium) in one machine on a mobile coach for displaying information, occasionally user might change chuck in some data into mongodb.

Now, the power supply of the machine is constant, coach driver may power off the machine at any time. machine has 2 partition, first is aufs for /, the other is ext4 for mongodb /data directory. BUT during the instant of power cut, there is no data input into the db.

Problem:

Every time the machine is restarted due to power cut (every several hours), mongodb will leave a mongod.lock file in its directory. in /etc/rd.local I have tried to delete the lock file every boot up, but it sometimes still refuse to start. which causing my app fail the start.

According to official docs: http://www.mongodb.org/display/DOCS/Durability+and+Repair , I still have some occasion unable to start.

What's the best practice to run mongodb in a regular power failure situation like above? Without throwing additional hardware.

some presentation declares that zfs has:

zfs can detect and correct silent data corruption.

e.g. from here http://www.eecis.udel.edu/~bmiller/DE-OSUG/ECECIS-ZFS.pdf

1. But do you need to allocate some spare disk or zfs pool to do it mannually? or this is intrinsic by zfs?
2. Does single disk zfs file system have this feature or you have to get RAIDZ?

I'm going to build a freenas server, would like to make sure what I can do with such magical and advanced zfs.

If I have 5 * 3TB disks in RAIDZ (12TB storage in total), now I am trying to add another 2 * 3TB disks to this existing array.

Q:

1. Am I able to do it without affect/touch any existing data on RAIDZ volume?
2. What about take away some existing disk? say take away 1 disk out of the 5 disks, assuming only very small portion of data exists on the raidz.

I have a 300G Western Digital Raptor, recently showing UNC SMART, wondering anyone who has experience knows should I replace it and get warranty form WD?

Details of smartctl -a as follows:

smartctl 5.41 2011-06-09 r3365 [FreeBSD 8.2-RELEASE-p6 amd64] (local build)
Copyright (C) 2002-11 by Bruce Allen, http://smartmontools.sourceforge.net

=== START OF INFORMATION SECTION ===
Model Family:     Western Digital VelociRaptor
Device Model:     WDC WD3000HLFS-01G6U0
Serial Number:    WD-WXD0C79C8807
LU WWN Device Id: 5 0014ee 0ac3cfaf0
Firmware Version: 04.04V01
User Capacity:    300,069,052,416 bytes [300 GB]
Sector Size:      512 bytes logical/physical
Device is:        In smartctl database [for details use: -P show]
ATA Version is:   8
ATA Standard is:  Exact ATA specification draft version not indicated
Local Time is:    Thu Apr 19 16:03:33 2012 CST
SMART support is: Available - device has SMART capability.
SMART support is: Enabled

=== START OF READ SMART DATA SECTION ===
SMART overall-health self-assessment test result: PASSED

General SMART Values:
Offline data collection status:  (0x84) Offline data collection activity
                    was suspended by an interrupting command from host.
                    Auto Offline Data Collection: Enabled.
Self-test execution status:      (   0) The previous self-test routine completed
                    without error or no self-test has ever 
                    been run.
Total time to complete Offline 
data collection:        ( 4800) seconds.
Offline data collection
capabilities:            (0x7b) SMART execute Offline immediate.
                    Auto Offline data collection on/off support.
                    Suspend Offline collection upon new
                    command.
                    Offline surface scan supported.
                    Self-test supported.
                    Conveyance Self-test supported.
                    Selective Self-test supported.
SMART capabilities:            (0x0003) Saves SMART data before entering
                    power-saving mode.
                    Supports SMART auto save timer.
Error logging capability:        (0x01) Error logging supported.
                    General Purpose Logging supported.
Short self-test routine 
recommended polling time:    (   2) minutes.
Extended self-test routine
recommended polling time:    (  59) minutes.
Conveyance self-test routine
recommended polling time:    (   5) minutes.
SCT capabilities:          (0x303f) SCT Status supported.
                    SCT Error Recovery Control supported.
                    SCT Feature Control supported.
                    SCT Data Table supported.

SMART Attributes Data Structure revision number: 16
Vendor Specific SMART Attributes with Thresholds:
ID# ATTRIBUTE_NAME          FLAG     VALUE WORST THRESH TYPE      UPDATED  WHEN_FAILED RAW_VALUE
  1 Raw_Read_Error_Rate     0x000f   195   195   051    Pre-fail  Always       -       49036
  3 Spin_Up_Time            0x0003   199   196   021    Pre-fail  Always       -       3008
  4 Start_Stop_Count        0x0032   100   100   000    Old_age   Always       -       425
  5 Reallocated_Sector_Ct   0x0033   200   200   140    Pre-fail  Always       -       0
  7 Seek_Error_Rate         0x000e   200   200   000    Old_age   Always       -       0
  9 Power_On_Hours          0x0032   086   086   000    Old_age   Always       -       10292
 10 Spin_Retry_Count        0x0012   100   100   000    Old_age   Always       -       0
 11 Calibration_Retry_Count 0x0012   100   100   000    Old_age   Always       -       0
 12 Power_Cycle_Count       0x0032   100   100   000    Old_age   Always       -       404
192 Power-Off_Retract_Count 0x0032   200   200   000    Old_age   Always       -       268
193 Load_Cycle_Count        0x0032   200   200   000    Old_age   Always       -       426
194 Temperature_Celsius     0x0022   117   100   000    Old_age   Always       -       30
196 Reallocated_Event_Count 0x0032   200   200   000    Old_age   Always       -       0
197 Current_Pending_Sector  0x0012   200   200   000    Old_age   Always       -       0
198 Offline_Uncorrectable   0x0010   200   200   000    Old_age   Offline      -       4
200 Multi_Zone_Error_Rate   0x0008   200   200   000    Old_age   Offline      -       1

SMART Error Log Version: 1
ATA Error Count: 749 (device log contains only the most recent five errors)
    CR = Command Register [HEX]
    FR = Features Register [HEX]
    SC = Sector Count Register [HEX]
    SN = Sector Number Register [HEX]
    CL = Cylinder Low Register [HEX]
    CH = Cylinder High Register [HEX]
    DH = Device/Head Register [HEX]
    DC = Device Command Register [HEX]
    ER = Error register [HEX]
    ST = Status register [HEX]
Powered_Up_Time is measured from power on, and printed as
DDd+hh:mm:SS.sss where DD=days, hh=hours, mm=minutes,
SS=sec, and sss=millisec. It "wraps" after 49.710 days.

Error 749 occurred at disk power-on lifetime: 6972 hours (290 days + 12 hours)
  When the command that caused the error occurred, the device was active or idle.

  After command completion occurred, registers were:
  ER ST SC SN CL CH DH
  -- -- -- -- -- -- --
  40 51 00 44 cb 53 40  Error: UNC at LBA = 0x0053cb44 = 5491524

  Commands leading to the command that caused the error were:
  CR FR SC SN CL CH DH DC   Powered_Up_Time  Command/Feature_Name
  -- -- -- -- -- -- -- --  ----------------  --------------------
  60 40 10 a6 4e 58 01 08      00:16:23.812  READ FPDMA QUEUED
  60 08 10 9e 32 5b 00 08      00:16:17.646  READ FPDMA QUEUED
  60 08 10 9e 32 5b 00 08      00:16:17.645  READ FPDMA QUEUED
  ef 02 00 00 00 00 00 08      00:16:17.645  SET FEATURES [Enable write cache]
  60 08 10 9e 32 5b 00 08      00:16:11.412  READ FPDMA QUEUED

Error 748 occurred at disk power-on lifetime: 6972 hours (290 days + 12 hours)
  When the command that caused the error occurred, the device was active or idle.

  After command completion occurred, registers were:
  ER ST SC SN CL CH DH
  -- -- -- -- -- -- --
  40 51 00 44 cb 53 40  Error: UNC at LBA = 0x0053cb44 = 5491524

  Commands leading to the command that caused the error were:
  CR FR SC SN CL CH DH DC   Powered_Up_Time  Command/Feature_Name
  -- -- -- -- -- -- -- --  ----------------  --------------------
  60 08 10 9e 32 5b 00 08      00:16:11.412  READ FPDMA QUEUED
  60 08 10 9e 32 5b 00 08      00:16:11.412  READ FPDMA QUEUED
  ef 02 00 00 00 00 00 08      00:16:11.412  SET FEATURES [Enable write cache]
  60 00 30 1e cb 53 06 08      00:16:05.199  READ FPDMA QUEUED
  60 00 30 1e cb 53 06 08      00:16:05.180  READ FPDMA QUEUED

Error 747 occurred at disk power-on lifetime: 6972 hours (290 days + 12 hours)
  When the command that caused the error occurred, the device was active or idle.

  After command completion occurred, registers were:
  ER ST SC SN CL CH DH
  -- -- -- -- -- -- --
  40 51 00 44 cb 53 40  Error: UNC at LBA = 0x0053cb44 = 5491524

  Commands leading to the command that caused the error were:
  CR FR SC SN CL CH DH DC   Powered_Up_Time  Command/Feature_Name
  -- -- -- -- -- -- -- --  ----------------  --------------------
  60 00 30 1e cb 53 06 08      00:16:05.199  READ FPDMA QUEUED
  60 00 30 1e cb 53 06 08      00:16:05.180  READ FPDMA QUEUED
  60 00 30 1e cb 53 06 08      00:16:05.178  READ FPDMA QUEUED
  60 00 30 1e cb 53 06 08      00:16:05.178  READ FPDMA QUEUED
  60 00 30 1e cb 53 06 08      00:16:05.178  READ FPDMA QUEUED

Error 746 occurred at disk power-on lifetime: 6972 hours (290 days + 12 hours)
  When the command that caused the error occurred, the device was active or idle.

  After command completion occurred, registers were:
  ER ST SC SN CL CH DH
  -- -- -- -- -- -- --
  40 51 00 44 cb 53 40  Error: UNC at LBA = 0x0053cb44 = 5491524

  Commands leading to the command that caused the error were:
  CR FR SC SN CL CH DH DC   Powered_Up_Time  Command/Feature_Name
  -- -- -- -- -- -- -- --  ----------------  --------------------
  60 00 30 1e cb 53 06 08      00:15:58.945  READ FPDMA QUEUED
  60 00 30 1e cb 53 06 08      00:15:58.945  READ FPDMA QUEUED
  60 00 30 1e cb 53 06 08      00:15:58.945  READ FPDMA QUEUED
  60 00 30 1e cb 53 06 08      00:15:58.945  READ FPDMA QUEUED
  60 00 30 1e cb 53 06 08      00:15:58.944  READ FPDMA QUEUED

Error 745 occurred at disk power-on lifetime: 6972 hours (290 days + 12 hours)
  When the command that caused the error occurred, the device was active or idle.

  After command completion occurred, registers were:
  ER ST SC SN CL CH DH
  -- -- -- -- -- -- --
  40 51 00 44 cb 53 40  Error: UNC at LBA = 0x0053cb44 = 5491524

  Commands leading to the command that caused the error were:
  CR FR SC SN CL CH DH DC   Powered_Up_Time  Command/Feature_Name
  -- -- -- -- -- -- -- --  ----------------  --------------------
  60 00 30 1e cb 53 06 08      00:15:52.727  READ FPDMA QUEUED
  60 00 30 1e cb 53 06 08      00:15:52.727  READ FPDMA QUEUED
  60 00 30 1e cb 53 06 08      00:15:52.727  READ FPDMA QUEUED
  60 00 30 1e cb 53 06 08      00:15:52.727  READ FPDMA QUEUED
  60 00 30 1e cb 53 06 08      00:15:52.726  READ FPDMA QUEUED

SMART Self-test log structure revision number 1
No self-tests have been logged.  [To run self-tests, use: smartctl -t]


SMART Selective self-test log data structure revision number 1
 SPAN  MIN_LBA  MAX_LBA  CURRENT_TEST_STATUS
    1        0        0  Not_testing
    2        0        0  Not_testing
    3        0        0  Not_testing
    4        0        0  Not_testing
    5        0        0  Not_testing
Selective self-test flags (0x0):
  After scanning selected spans, do NOT read-scan remainder of disk.
If Selective self-test is pending on power-up, resume after 0 minute delay.

I have a special demand that to improve the redundancy of a network. (any of the cable between switches broken will NOT disconnect any clients)

   S = a switch    C = a computer   - = CAT5 cable

                  Internet
                     |
                  ROURTER              C
                     |                /
         S---S---S---S---S---S---S---S--C
         |                       |
      C--S---S---S---S---S---S---S
         /
        C

This seems should work, but:

1. Does it work just out of the box?
2. Any settings needed? (on router? or pc?)
3. Will a packet gets passed around infinitely?

Thanks guys!

When previous boot was failed. (because of power failure, hardware failure) booting will hang at the grub menu for human prompt.

Can you set option to force boot up no matter what happened?

Hi I have an untangle server in my office with 443(web-interface) and 1194(openvpn port) forwarded to this machine.

Can you configure only 1 NIC for untangle and use it as openvpn server?

Possible Duplicate:
What are the cons to using a PC/cheap PCs as servers vs hardware designed to be used for servers?

I would like to build some my rack servers based on commodity pc components, which would be and cheaper and better performance with same amount of money spent

In face I have already built 2 i7-920 two years ago with stock cooling system. and they all happily running, haven't had single failure and manual force reboot.

Could there be any potential problems?
does commodity pc has higher failure rate than branded server and server components?

My domain email can be handled by the google. by setting mx record and stuff to google.

but i would like to have my linux server to send email to the world and not treated as spam, is it possible?