-----Original Message-----
From: Boris Bakchiev [mailto:[EMAIL PROTECTED]
Sent: Tuesday, June 13, 2006 2:13 AM
To: Asterisk Users Mailing List - Non-Commercial Discussion
Subject: RE: [Asterisk-Users] Hard drive write cache
These days you don't have to worry much about your write
cache unless you're running application where once single
byte changed will affect whole file.
Look at it this way, the only corruption will occur is
whatever the files were open by asterisk at the time of the
crash. And only up to the point where the file was last open.
As far as I know asterisk does not keep cdr or log files open
so you would loose only the data that was written at the time
of the power failure.
Any journaling file system (ext3, resierfs, xfs, etc) will
easily handle any power failure event. Your files will not be
corrupt but could miss some of the data.
At the most you will loose 10-50 cdr entries written to you log files.
If you post CDR to a remote SQL database then you asterisk
install and linux is more or less static and will not be
affected by the power failure.
What you need to do is minimise the writes to hard disk's:
1 - Send syslog to remote server and do not do ANY syslogs
Or keep the circular buffer in memory if you have plenty of it.
2 - Send CDR's to SQL server (or log to ramdisk and send to
remote server every few minutes via SSH)
3 - Do not record any calls (or do that somewhere else)
4 - Stop any services that write/read data on regular intervals.
If you have no writes you have nothing to worry about during
power failure and journaling file system will take care of the rest.
Keep your partition size really small so that fsck will not
take much time.
You have to be realistic, you cannot achieve 99.999% uptime.
That's 5 minutes per year downtime.
You will have more or less 100% until your first hardware failure.
Even if you have all the hardware components pre-purchased it
will still take you 2-12 hours to detect, diagnose and fix
the fault if you lucky.
So your 5 minuets
If the business is demanding 99.999% then it should be
prepared to invest into the hardware.
I would recommend a cluster or even better a fault tolerant server.
Those are expensive but you can pretty much rule out the
hardware failure and swap all of the failed components while
the system is running (cpu, memory, hdd, etc).
Look at Stratus or NEC FT servers if you need hardware redundancy.
They're expensive but will give you the hardware reliability you need.
Or get a traditional PABX :)
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:asterisk-users-
[EMAIL PROTECTED] On Behalf Of shadowym
Sent: Tuesday, 13 June 2006 10:34
To: asterisk-users@lists.digium.com
Subject: [Asterisk-Users] Hard drive write cache
I am looking at ways to harden my asterisk install to
prevent computer
related issues from happening. I am concerned about about
disk write
cache.
That seems to be a major source of hard drive corruption on power
failure.
Hard Drive corruption is simply unacceptable for the 99.999% uptime
requirements of my Asterisk install that needs to be as
reliable as a
proprietary PBX.
Of course I will be using redundant power supplies, raid 1 and use a
UPS.
None of those things mean much if the power cords accidentally get
pulled
from the back of the server. Unlikely as it may be I have
to consider
ALL
possibilities.
So is disabling the write cache a good way to reduce the
risk of hard
drive corruption for an Asterisk server? I am not too
concerned about
the reduced performance/lifetime of hardrives with write cache
disabled since
Asterisk
is not a very write intensive environment. Even with lot's of
voicemail
going on.
Any other recommendations/links for increasing the reliability of
Asterisk
servers?
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