| Best File System for Kerio Connect (Performance and Consistency) [message #119356] |
Thu, 12 February 2015 23:57  |
amedina
Messages: 16
Registered: April 2009
Location: Santo Domingo
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Hi All,
recently we had a problem with the data partition on our Kerio Connect server, the partition had a serious corruption and some data was lost.
A couple of month ago we had several power loss on our data center and the server was turned off abruptly, this happened a couple of times during working hours in the past months.
Those times, when the power was recover, the server was turned on and everything continue working good untill this week. The data partition had an EXT4 filesystem, Do you think this corruption could be caused for those power outages?
We resolved the problem with the power outage on our Datacenter, but now that I have to create a new partition, which filesystem could you recommend for use with Kerio Connect? I have read that ReiserFS is good for working with a lot of files and for performance, but I don't know how it is with power outages (we resolved the power problem, but in the case it happen again).
Thanks and best regards.
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| Re: Best File System for Kerio Connect (Performance and Consistency) [message #119412 is a reply to message #119359] |
Sun, 15 February 2015 13:44  |
Maerad
Messages: 275
Registered: August 2013
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The Problem is Not the file system, it's the missing usv and/or raid system with a bbu or fbwc. If the server loses power and it it writes data to the hdd in that instant, the cached data still to write is lost and the file system broken. Normally you have a usv on your server, reporting a power loss to the server, keeping it up with battery power so the server can shut down gracefully.
No file system can prevent something like a sudden data loss because of a power shortage. Maybe if you disable any kind of caching, but the performance will be absurdly low.
Get a bbu or fbwc for you raid card (or a raid if you don't even have that) and a usv. Then configuration the usv. To shutdown the server when power is lost. There won't be any data failures I the future then. Well, a daily backup is still something you need.
I'm quite a bit shocked that you call it a data center if there's not even the most basic protection available in it...
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| Re: Best File System for Kerio Connect (Performance and Consistency) [message #119431 is a reply to message #119412] |
Mon, 16 February 2015 20:09 |
amedina
Messages: 16
Registered: April 2009
Location: Santo Domingo
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Hi and thank you all for your replies,
Our server have Hardware raid (poweredge r510) with RAID 10, and dual power supplies. In my country the electrical supply isn't very good, and we have a power generator and an UPS for the server. In those days we was out of luck (apparently), the UPS crashed and a couple of days later the power generator failed, that's why the server was shut down abruptly.
I made the question because I had read that in EXT4 some features from EXT3 that were removed for a better performance that may cause that kind of failures with power loss.
I'm really sorry if I misused the name "Data Center", if you prefer you can read it as "the place where we have some servers"
Thank you in advanced for you replies!
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| Re: Best File System for Kerio Connect (Performance and Consistency) [message #119435 is a reply to message #119431] |
Mon, 16 February 2015 23:33 |
Maerad
Messages: 275
Registered: August 2013
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amedina wrote on Mon, 16 February 2015 20:09
Our server have Hardware raid (poweredge r510) with RAID 10, and dual power supplies. In my country the electrical supply isn't very good, and we have a power generator and an UPS for the server. In those days we was out of luck (apparently), the UPS crashed and a couple of days later the power generator failed, that's why the server was shut down abruptly.
I made the question because I had read that in EXT4 some features from EXT3 that were removed for a better performance that may cause that kind of failures with power loss.
Ah, ok. I feared for the worst 
Please check if your server has a battery unit or fbwc for the raid card (if yes, check if ok with idrac) - if not, buy one ASAP. The battery or fbwc hold the data that still need to be written from the controller to the hdds in the cache till the power is resumed. That way, even with the failure of the UPS it wont kill your raid.
And that's the second thing - you should by all means use ext4. It's quite better then ext3 and ext3 should only be used for compatiblity issues. You can disable some things in ext4 that make it faster, but less harden against errors. But usually all important features are turned on.
But honestly, the file system dosn't really matter - your problem with the power is that the raid controller can't write everything to the disks and in case that happens, it kills the raid or important partitions of it. That is below the file system, so even with a awesome one, it wouldn't change the fact that the data gets lost. Of course, if the OS wanted to write something or kerio was writing a mail to the hdd and wasnt finished to prepare the data for the cache it's also a loss. But that's something your filesystem or OS can fix.
Some ideas what you could do to improve the dataloss protection:
- Get a second (cheap) server in hardware, virtualise everything and do a "live" backup with something like hyperv replica (forgot the name of the vmware product). That way, even if the main raid fails, theres a live backup on the second server.
- If the USV it is a managable one - only allow the server to get power if the usv is at least at 80%. Or get a second one you can turn on if the other is on low power.
- Change the raid controller to more "Data protection" instead of "performance" and maybe use another raid typ that is more forgiving in a case of dataloss/write problems. Will hit the speed, but better slow then missing files :3
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