On 1/28/2015 11:07 PM, John R Pierce wrote: > On 1/28/2015 4:32 AM, Jatin Davey wrote: >> I am using RHEL 6.5 on my server. >> >> From top command i can see that the processors in my server are >> spending a lot of time on wait for I/O. >> I can see high percentage in terms of 30-50% on "wa" time. >> >> Here is the df output about the disk space in my system: >> >> ********** >> [root at localhost images]# df >> Filesystem 1K-blocks Used Available Use% Mounted on >> /dev/sda1 1915071844 103227908 1714563936 6% / >> tmpfs 32931472 0 32931472 0% /dev/shm >> ********** >> >> Could someone point me on how to improve the disk I/O on my server >> and reduce the wait time on I/O. > > it appears you have everything on a single file system on a single 2TB > drive? [Jatin] Yes , entire disk is mounted on a single file system. Will this cause high wait time for I/O operations ? Do you think splitting it into multiple partitions would help ? Appreciate if you can enlighten me in this regard or provide pointers to it. > I'm going to guess thats a desktop grade SATA disk spinning at most at > 7200rpm (many are slower, 'green' disks are often 5400rpm). [Jatin] Yes , it is a SATA disk. I am not sure of the speed. Can you tell me how to find out this information ? Additionally we are using RAID 10 configuration with 4 disks. > > what sort of workload are you running? [Jatin] Our workload is a bit high on disk reads / writes and hence i am seeing slowness in it when using the top command. We basically run VMs on the RHEL 6.5 host. Our target is to house 5-6 application VMs on this host and ship this as a product on a rack server. > our high disk IO servers, doing things like transactional databases, > have many 10000rpm or 15000 rpm drives on a SAS2 raid card with 1GB or > 2GB of write-back-cache (battery or flash backed). > > Hi John Please see my responses inline. Appreciate your inputs in this regard. Thanks Jatin