dma not enabled?

[mattsoftnet]

I have a vmware server running on a dual core amd 4850. I'm using a 500gb sata for the main driv, but the system seems like it suffers badly from poor disk performance. I think dma is disabled. it is very fustrating having these problems with linux and not being able to find a relative answer anywhere. I'm hoping someone can help me fix this. shouldn't dma be enabled by default and shouldn't it be 32 or 64 bit not 16?

# /sbin/hdparm /dev/sda

/dev/sda:

IO_support = 0 (default 16-bit)

readonly = 0 (off)

readahead = 256 (on)

geometry = 60801/255/63, sectors = 976773168, start = 0

# lspci | grep -i sata

00:09.0 IDE interface: nVidia Corporation MCP78S SATA Controller (non-AHCI mode) (rev a2)

#

[mattsoftnet]

any help please?

root@localhost ~# hdparm -d1 /dev/sda

/dev/sda:

setting using_dma to 1 (on)

HDIO_SET_DMA failed: Inappropriate ioctl for device

when I installed centos on the server, I had to use pci=nomsi to get it to install. I don't know why that is needed or what exactly it does, but could that have anything to do with my performance problem?

[AndreTheGiant]

The hdparm utility was designed for IDE (PATA) disks.

So could be normal that on most SATA disk does not work.

See: http://www.linuxquestions.org/questions/linux-hardware-18/sata-drives-and-dma-458088/

Andre

[mattsoftnet]

I haven't a clue if I'm right or not, but from what I've read, sata doesn't need dma turned on, it's enabled by default in the sata specs and can't be turned off. if that's true then that's good because I don't have to worry about it. but there is still a performance issue on my vmware server.

does this look right?

root@localhost ~# hdparm -Tt /dev/sda

/dev/sda:

Timing cached reads: 2272 MB in 2.00 seconds = 1135.89 MB/sec

Timing buffered disk reads: 194 MB in 3.01 seconds = 64.50 MB/sec

root@localhost ~#

what is the best way to tell how much memory is REALLY being used on my vmware server? there are so many needless complexities in linux. I don't know if what I see if top or htop is accurate or even relavent to what I need to know about the system.

[AndreTheGiant]

but there is still a performance issue on my vmware server.

The hdparm -T results are normal-good for a SATA disk.

To see memory usage you can use esxtop (it is useful also for a lot of other parameters) or performance monitor from VIC.

Andre