Use Of Shared Storage In High Availability Arrays? 18
urbanjunkie asks: "I want to ensure my web site/database farm/whatever is as available as possible, so I checked out many HA (High Availability) packages for Linux. It seems that they -all- seem to want me to use shared storage. I don't want to use shared storage since it moves the point of failure to the disk array. I know that the disk array can be RAIDed etc, but what about a fire, power loss and any of the other things that can go wrong? I'd prefer to have something that replicated changes made to one disk to another disk located in a separate PC that may well be in a location 100 metres away. Is there anything open sourced that can do this?"
Try OpenAFS (Score:2)
Re:Try OpenAFS (Score:2)
HighAvailibility or Replication (Score:1)
duh (Score:1)
Stick with shared storage... (Score:2)
For the sake of specs, the thing takes 9 SCSI disks, using FC/AL for linkup, and works with Linux and Solaris (among other systems I believe). Placing 2 together DOES NOT make a RAID5+1 array, the whole thing is straigh RAID5. The systems also have 256 MB of RAM to remove the RAID5 write penalty. Should a catastrophic failure occcur (all power to the box kicks), internal UPSes will dump the info in the RAM to the disks and power down correctly.
The investment is definitely worth it, and makes things easier than other systems. As for fire damage, get a Halon system and BACKUP YOUR DATA!
If you're really paranoid, you can seperate the boxes a little...
My karma's bigger than yours!
Kind of vague question, but good topic anyway (Score:1)
Tivoli (Score:1)
cousin (Score:1)
Re:Stick with shared storage... (Score:2)
I don't think that you really get it. It _still_ has a _single_ point of failure, and it's a pretty large point, the whole box. Urbanjunkie is asking for a solution that will allow service to continue even if a whole box (any box) is destroyed.
Think earthquake. Then design a network layout and set of systems that would withstand the total destruction of any system in the network. That's what urbanjunkie is asking for.
Database replication can be nasty business. It all comes down to the failure modes. Things like distributed transactions can have some pretty nasty ones. No, I don't have a solution. :) If your period between updates is high, you can try having one authoritative system. You perform all your updates to it, and then periodically shut it down and copy the files to the remote servers.
Jason PollockRe:Stick with shared storage... (Score:3)
I guess it's how much availability you want. That last 0.001% drives costs through the roof. Many modern disk arrays have everything redundant and hot swappable, including not just disk modules, but power supplies, fans, and controllers.
Set up a nice HA disk array and cluster the servers and you too [microsoft.com] can run all of your critical services on one subnet!
Yes, there is. (Score:2)
Yes, rsync. http://rsync.samba.org [samba.org]
-Peter
"There is no number '1.'"
Multi-Path (Score:1)
There are of course other options, and <SHAMELESS PLUG> you can have the company I work for work out a solution for you. Check out our website at http://www.missioncriticallinux.com/ and then call our professional services department </SHAMLESS PLUG>
Good luck.
Re:WTF (Score:1)
Replicated filesystems (Score:1)
The main problem with this stuff is that it may not be ready for production use yet.
Ade
Re:duh (Score:1)
EMC (Score:2)
Disclaimer: I work for EMC.
There has to be a free equivalent out there (Score:1)
I was working a place that needed a HA product for NT. Most of the products wanted shared storage or used a file level replication that were either not 100% reliable or had way too much overhead. We stumbled across Vinca's [vinca.com] Co-Standby Server. It establishes a 2-node cluster with a 100Mb, Fiber, etc. link between them. I realize that several packages do this but I think this one had a couple things going for it. The data had to be on a seperate physical disk or volume(s) and copied on a block level. You need 2 seperate disks or volume(s) if you wanted to fail over either direction (system, data and mirror for other system) or if you only had 2 disks you can do a fall back from to the other. You setup virtual IP addresses, shares, etc. and the other machine will assume it's identity if it doesn't answer in the time you tell to. We only rebooted our servers 1 time for SP4 in the year I was there after they were setup.
I'm not telling the poster that he should look into this non-open $3000-$4000 software on NT. What I am saying is that if a similar type of setup was done on a *nix setup then it would be about as bullet-proof as you can get on a commodity x86 box. I'm talking about a product from 3 years ago for NT. Surely someone can create a similar product on Linux/BSD/Etc..
To answer the whiners before they start: I would do this myself if I could but I have been severly handicapped by starting with NT. I've got a lot of retraining to do before I could help out with something like this.
Solaris HA solution (Score:2)
Currently, we're running a pair of Sun E4500's (4 CPU 6 gig 2 disk boards 2 IO boards) connected to a pair of Sun StorEDGE A5200 disk arrays by FCAL. Each box has 2 fiber connections to each array, for a max throughput to the box of 2gbit. The 4500's are running Solaris 7 for OS, Veritas Volume Manager for managing disk storage, and Veritas Cluster Server for HA management of Oracle 8.
Veritas won't let both machines mount the disks at the same time (which would be bad anyway), and it does a rather good job of managing things. Recently when we had a cpu die in the primary machine, the cluster failed over and had Oracle up (and running recovery) in 1 minute 3 seconds. Not bad, considering the other box rebooted itself and didn't shut Oracle down cleanly.
-j