Jason L. Froebe: Ramblings of a Geek

A few weeks ago I mentioned having troubles with direct i/o and ASE, ASE 15.0.1 esd 2 on Linux with direct i/o woes.  Guess what?  I solved the problem!

It ended up being the driver for the Areca ARC-1110 PCI-X RAID Card. Using the driver obtained from Areca (ftp://ftp.areca.com.tw/RaidCards/AP_Drivers/Linux/DRIVER) I was able to reliably reproduce the problem. When I upgraded the kernel to 2.6.20 which includes a driver for the ARC-1110 RAID card, the problem went away. There appears to be a memory leak in the driver provided by Areca under certain circumstances such as ASE 12.5x, 15.x using O_DIRECTIO with lots of I/O. This memory leak will cause ASE to be killed by the kernel as the ASE process (dataserver) will appear to have eaten up all available memory. The driver included in the v2.6.19 and higher kernels don’t seem to have this problem in my testing.

I’ve asked Sybase TechSupport to “Please create a solved case explaining that if the ASE process is killed by the kernel (it will be in /var/log/messages), then quite likely the cause is a driver issue.“

I opened a case with Sybase Technical Support that basically went like this:

When the access to the NAS device is accessed solely through a \\nas-device\ type, ASE will fail saying the device is invalid. While I can understand Sybase not wanting to support network drives, allowing a disk init on a NAS drive is necessary in lab/test/etc environments where the machine is maxed out on internal devices or other situations where there isn’t enough space on the local disks - inexpensive SAN devices that provide ‘\\nas-device\’ access is often the only way to go due to price or time constraints. Remember that months may pass between the purchase of a SAN array and having it made available to the dba team.

Sybase TechSupport was able to verify that the disk init actually did work but they weren’t able to reproduce the problem. This caused me to perform a thorough investigation as to why the disk init was failing.

I discovered the root cause. ASE v12.5.4 esd 5 and v15.0.1 esd2 will fail on disk init for some *LINUX* based NAS drives. An example of such a beast is the Western Digital My Book series (Network enabled): http://www.westerndigital.com/en/products/Products.asp?DriveID=318

The problem is that many Linux based NAS drives support only the bare essentials of the SMB protocol and rarely the current CIFS protocols.  As I understand it, when WinXP, Win2k3, Vista attaches to a network drive, it will use CIFS by default and then revert to SMB if necessary.

Ultimately, Sybase ASE requires CIFS for the disk init to work correctly. So, before getting that inexpensive network device, make sure it uses CIFS and doesn’t use the ext2 file system internally.