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HA ftp server ...

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K.C. Chan
Trusted Contributor

HA ftp server ...

All,
I am looking into implementing an HA FTP server; I am looking at LVS, this looks promising. Have any one ever done this before? Does any one have any suggestions?

In regards to LVS, in my case, implementing HA ftp server, I need to be able to share storage, either by replicating via some software (e.g: CODA file system) or via hardwared. I am interested in how someone handles the shared storage issue. Thanks.
Reputation of a thousand years can be determined by the conduct of an hour
9 REPLIES
Dave Falloon
Trusted Contributor

Re: HA ftp server ...

I've made some semi-HA clusters for less than critical systems using rsync to keep files up to date. You are vulnerable to lost data during sync's.

I have made a HA cluster using drbd that worked very nicely. I would recommend drbd to anyone looking to replicate data between two machines.

drbd homepage:

http://www.drbd.org/

If you have the money you could use shared scsi but the cost is pretty high and unecessary unless you need fast disks.

I hope that helps,

Dave
Clothes make the man, Naked people have little to no effect on society
K.C. Chan
Trusted Contributor

Re: HA ftp server ...

share scsi sounds interesting, could you recommend any url, I would like to read up on it. I'm interested in how many servers can share the the scsi interface and what kind of disk capacity is available. Thanks.
Reputation of a thousand years can be determined by the conduct of an hour
Ragu_1
Regular Advisor

Re: HA ftp server ...

Have implemented a sharing of storage using ENBD http://www.it.uc3m.es/ptb/enbd/. Deploying an enbd solution alongwith the HA package `heartbeat' has been quite effective.
Share and share alike
K.C. Chan
Trusted Contributor

Re: HA ftp server ...

How about server requirements, cpu and memory? Any suggestions on rule of them when selecting such server?
Reputation of a thousand years can be determined by the conduct of an hour
Dave Falloon
Trusted Contributor

Re: HA ftp server ...

From what I have gathered on shared scsi you can end up with SPOF's ( Single point of failure ) in the scsi hardware controlling your storage. What are you ultimate goals on this project, low cost or highest performance?

Best I have seen with my own eyes using shared scsi was two boxes in an active passive HA cluster serving NFS. It was quick but expensive. If I remember correctly the scsi raid chassis filled with disks, with two scsi controllers was over $20 000 alone, then the two servers were over $10 000 each, with multiple aggregated gigE interfaces, it was smoking fast, but the price tag was pushing $50000.

Or you can make an HA cluster on the cheap out of spare parts. Take two identical older machines, say dual p3 800's with a gig of PC 133 ram each. Now take about 4 10/100 ethernet cards. Pop in a couple of disks, faster the better. Take three of the network cards and bond them together. Your kernel has to support the bonding driver. This is 802.3AD if I remember correctly, so you can read up on that spec to see whats going on in an aggregated ethernet link if you want. Here is a link to the IEEE web page:

http://grouper.ieee.org/groups/802/3/ad/

Now that you have a bonded ethernet link that should approach about 250 Mips on each server connect a pile of crossover cables between the servers. This is you interserver communication link that we are going to use for drbd to keep your disks sync'd. Get drbd working over this link, install your ftp server of choice. Also connect a serial cable between the boxes so you can halt the machine if the network croaks. Make sure to run some kind of STONITH script so that a failing machine can't take you out. That should be plenty HA enough for a small time ftp server.

Might be something worth looking at:

http://www.linux-ha.org/

Loads of good ideas.

I hope that helps.

Dave
Clothes make the man, Naked people have little to no effect on society
Dave Falloon
Trusted Contributor

Re: HA ftp server ...

Woops I forgot to give you a link for shared scsi:

http://www.ibiblio.org/pub/Linux/ALPHA/linux-ha/High-Availability-HOWTO-7.html

Thats a quick one I found giving you an over view of whats going on with shared scsi

Dave
Clothes make the man, Naked people have little to no effect on society
K.C. Chan
Trusted Contributor

Re: HA ftp server ...

Dave, thanks for your input. I touch base with the powers to be, what he meant by HA = stable ftp server.

BTW, the cheap HA setup sounds interesting. I will follow up with your url. Thanks.
Reputation of a thousand years can be determined by the conduct of an hour
Martin P.J. Zinser
Honored Contributor

Re: HA ftp server ...

As for a relatively low-cost shared storage solution with good built-in redundancy, check the MSA1000 fiberchannel array from hp.
Dave Falloon
Trusted Contributor
Solution

Re: HA ftp server ...

The cheap Ha dumper from one server to another is really worth the time. It has saved my butt more than once. Another benefit is that if something drops out in the middle of the night you just have to verify that the switch over happened and then you can fix the problem the next day. Saves you having to come in to work straight from the bar ... :)

Nothing like a drunking typo to ruin your week:

mv /tmp/foo /tmp/bar

can easily become

rm /

:)

I hope that helps,

dave
Clothes make the man, Naked people have little to no effect on society