[CentOS] Very slow disk I/O
Jatin Davey
jashokda at cisco.com
Thu Jan 29 12:55:05 UTC 2015
On 1/29/2015 4:50 AM, Gordon Messmer wrote:
> On 01/28/2015 04:32 AM, Jatin Davey wrote:
>> Could someone point me on how to improve the disk I/O on my server and
>> reduce the wait time on I/O.
>
> Start by identifying your disk and controller. Assuming that this is
> a single SATA disk:
>
> # smartctl -a /dev/sda | egrep 'Model:|Rate:|SATA Version'
[Jatin]
[root at localhost images]# smartctl -a /dev/sda | egrep 'Model:|Rate:|SATA
Version'
[root at localhost images]#
> # lspci | grep SATA
[Jatin]
[root at localhost images]# lspci | grep SATA
00:11.4 SATA controller: Intel Corporation Wellsburg sSATA Controller
[AHCI mode] (rev 05)
00:1f.2 SATA controller: Intel Corporation Wellsburg 6-Port SATA
Controller [AHCI mode] (rev 05)
> Next install and run iotop. If there's something on your system
> that's particularly active and unnecessary, disable it.
>
> If everything contending for your disk *is* necessary, then you may
> need to take steps to improve disk performance. There are a number of
> possibilities.
>
> 1: Use an SSD instead of a disk.
>
> 2: Use an SSD in addition to a disk. If a purely SSD storage system
> is too expensive, you might choose to use an SSD for one or more
> filesytems that you can mount where the high volume IO is occurring,
> and continue to use the disk for filesystems that need more data
> capacity and fewer IOPS.
[Jatin]
Thanks for these inputs. I will surely take it up with my team to see if
we can incorporate new hardware for our product.
>
> 3: Use a fast RAID array. A RAID1 array can provide better read
> performance than a single disk. For higher write volumes, use RAID10
> on four or more disks. Avoid RAID 5 or 6, as they'll be slower than a
> single disk.
[Jatin]
We are using RAID 10 in our server with 4 disks.
>
> 4: Replace poorly supported hardware. It might be that your SATA
> controller isn't well supported, and performs badly as a result. I
> used to have a desktop system with NVidia motherboard chipset. Its
> SATA controller was garbage. Performance with the same disk was
> noticeably better with a cheap PCI-E SATA controller.
>
>
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Hi Gordon
Please see my responses inline to your questions.
Appreciate your inputs in this direction.
Thanks
Jatin
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