Unsolved
This post is more than 5 years old
470 Posts
0
10680
bottlenecks
I have almost nothing on my ps4000. but some domain controllers are on it. exchange servers are authenticating through these servers and MS support is saying that I have disk porformance issues.
so I monitored the san volume on which the dcs are on for 3 days and here is what I have. Is there a bottleneck?
Anonymous
5 Practitioner
5 Practitioner
•
274.2K Posts
1
December 17th, 2011 11:00
Based on that data you don't have a SAN performance problem. I suspect you have Nagle and/.or Delayed ACK enabled on the server. This can cause artificial latency because the server is holding on to packets and delaying ACKs on writes.
to implement this workaround in ESX 4.x or 5.0, use the vSphere Client to disable delayed ACK.
Disabling Delayed Ack in ESX 4.x or 5.0
1. Log in to the vSphere Client and select the host.
2. Navigate to the Configuration tab.
3. Select Storage Adapters.
4. Select the iSCSI vmhba to be modified.
5. Click Properties.
6. Modify the delayed Ack setting using the option that best matches your site's needs, as follows:
Modify the delayed Ack setting on a discovery address (recommended).
A. On a discovery address, select the Dynamic Discovery tab.
B. Select the Server Address tab.
C. Click Settings.
D. Click Advanced.
Modify the delayed Ack setting on a specific target.
A. Select the Static Discovery tab.
B. Select the target.
C. Click Settings.
D. Click Advanced.
Modify the delayed Ack setting globally.
A. Select the General tab.
B. Click Advanced.
(Note: if setting globally you can also use vmkiscsi-tool
# vmkiscsi-tool vmhba41 -W -a delayed_ack=0)
7. In the Advanced Settings dialog box, scroll down to the delayed Ack setting.
8. Uncheck Inherit From parent. (Does not apply for Global modification of delayed Ack)
9. Uncheck DelayedAck.
10. Reboot the ESX host.
Regards,
tdubb123
470 Posts
0
December 17th, 2011 13:00
sorry I have another question.
I am reading about turning on flowcontrol on the switches.
should receive and send be both on or send on only?
tdubb123
470 Posts
0
December 17th, 2011 13:00
ok I have changed the esx hosts and rebooted. I see that I currently run raid 5. how do I change it to raid 50?
Also what is a good benchmark for
avg latency
ave queue depth
avg i/o rate
ave iops?
thanks
Anonymous
5 Practitioner
5 Practitioner
•
274.2K Posts
1
December 17th, 2011 14:00
Re: RAID5, you would have to destroy the array then reconfigure it. There's no way to convert from RAID-5 to 50. You can go larger not smaller. If you have another member in the same pool and have enough free space, you can remove that member, which resets it and add it back in a R50. RAID50 is the minimum RAID type to use. RAID5 by it's nature is riskier and slower than RAID50/R10. Exchange/SQL really prefer R10.
Re: flowcontrol. Both send and receive should be enabled on the switch.
Re: Latency, etc. There is a section in the SANHQ manual and online help which discusses how to interpret information like that. All those numbers need to be interpreted. There's no absolute value. IO rate and MB/sec are based on blocksize and random vs. sequential.
Regards,