MySQL 5.0 Standard distribution is not working with Xsan on my Xserve.

Question

MySQL 5.0 Standard distribution is not working with Xsan on my Xserve.

Hello,
until now we have always used on our Xservers the MySQL 5.0 Standard distribution downloadable from www.mysql.com (thus not the MySQL 4.1 that is shipped with Mac OS X 10.4 Server) with its datadir located on an internal disk of the Xserve. Since we have recently set up our Xsan we should now migrate the MySQL datadir to a directory on our 4 Tb Xsan volume, but doing so MySQL 5.0 no longer starts and even a myisamchk complains that the FYI tables are not MyIsam tables (but they are, I just copied the whole "local" datadir to the Xsan volume).
I then tried to configure the "standard" MySQL 4.1 that Apple ships with Mac OS X Server so that it uses the datadir on the Xsan volume and it starts with no problems, but we need MySQL 5.0! The problem seems to be therefore an incompatibility between the MySQLCOM distribution and the Xsan volumes.
Our setup is: an Xserve G5 dual 2 GHz running Mac OS X 10.4.8 and Xsan 1.4.1, MySQL 5.0.26,.
I wish to know if anyone else has encountered similar problems and how this has been eventually fixed.

Thank you, Fabrizio

PowerMac G5 dual core 2.3 GHz, Mac OS X (10.4.6)

Posted on Dec 6, 2006 6:54 AM

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Answer 1

Nov 20, 2010 7:37 AM in response to Fabrizio La Rosa

Hi Fabrizio,

Why, specifically, do you wish to host your MySQL data on Xsan?

I actually think this is a bad idea -- Xsan has significantly higher latency than a local file system (Xsan has good throughput, but poor latency -- specifically because every file read that occurs incurs a TCP/IP hit for metadata). Xsan is great for big files, with sequential reads. It is not so great for lots of small I/Os. So unless your MySQL database is pretty much completely composed of large BLOB data, I would suspect performance is not going to be all that good.

Curious to know what would drive the need to do what you ask.

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Answer 2

Nov 20, 2010 7:37 AM in response to William Lloyd

Well, we actually have quite a few reasons to host the MySQL data on Xsan:
- concurrent access: among other data, the Xsan should also store some MySQL databases actually used by a single web server hosting many virtual hosts and user-managed folders that we want to "split" on two Xserves for both load balancing and failover purposes. The idea is to keep the configuration for all virtual hosts and user folders on both servers activating only one half of them per server, so that in case one server fails the other can easily take its place.
- space: we have more than 4TB on Xsan, versus the 250 GB mirrored disks of the Xserve. Our databases actually occupy few gigabytes, but they will surely grow in the future.
- money: our company paid more than 100.000 euros for 14 Xserve, 2 Xserve Raid units and 10 Xsan licenses, and we want to use them as much as possible.
- database: performance is not a big concern for us while affordability is mandatory. BTW, one of the larger and most frequently used databases is composed by large blobs of data (it's used to store PDF files).
We purchased all these Apple server products because we always loved Macs and their OS: I still think that Mac OS X is the perfect OS for desktops/notebooks and Mac OS X Server/Xsan running on the Xserve platform are a good and relatively cheap choice for video editing and HPC. But while time goes by and more and more (often inexplicable) problems occur on our Xservers under stress, I also guess that the Apple server line is not the better choice for what we need to do: web hosting, email and authentication services, DHCP, network traffic analysis, and so on, for a big university.
We had always used Sun servers with Solaris up to few years ago and they never gave us a single problem after many years of use (and misuse), then Mac OS X 10.0.4 was relased...

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Answer 3

Nov 20, 2010 7:37 AM in response to Fabrizio La Rosa

Xserves and OS X Server can do a very good job at what you want to do. However, I still feel that, for purposes of hosting a database, it may be better to use a couple servers and a switch to fail over services should it be necessary (you can re-map LUNs via a switch). It will give you the best performance, and it will give you active/passive failover.

This stuff is all possible, and it all works well, however it needs to be thought out correctly and set up correctly. Some details on how this would work are in the "high availability administration guide" on www.apple.com/server/documentation.

BTW on network traffic analysis... I know of a couple places that are using Xserves specifically for network data monitoring, because they were far, far faster than any other machine tested.

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Answer 4

Nov 20, 2010 7:37 AM in response to Fabrizio La Rosa

After two days of testing I have finally found the solution to my issue: the real problem was the MySQL version we were using, mysql-standard-5.0.26-osx10.4-powerpc-64bit, were the problem is just the 64-bit.
You would expect a 64-bit software to be optmized for a G5 machine, but in this case the 32-bit version of MySQL 5.0.27 (mysql-standard-5.0.27-osx10.4-powerpc) started with no problems with its data stored on our Xsan volume.

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