Disk Spindles vs Controller Cache

[gicti]

Hi,

Our client has a x3550 m5 with an the M5200 series Raid controller with the 1GB Battery backed up Flash/Cache upgrade.

The server has 7 10K SAS drives in a RAID 6 configuration.

Examining Vcenter status it seems that the server is getting close of 20ms recommended threshold for Disk latency.

Questions:

Would getting a 4GB BBU Flash/upgrade be good step to getting the Disk latency down ?  (It would be less expensive then getting an external disk shelf)

Is there a way to view Flash/Cache usage status ?

Thanks in Advance,

G

[dmeyner22]

What is this servers function?  Is it hosting VMs? I'm assuming it's part of a cluster of host?  What is on this server that you are experiencing disk latency issues?

There are potentially a lot of different ways to alleviate disk latency issues and Cache is one way, (Flash Cache)SSD disk or just SSD.  Though it's good to provide more information to get an understanding of the environment.

[gicti]

Hi,

Server hosts the following VMs:

1. Windows 2008 & Exchange 2010 - SBS 2011
2. Windows 2008 Email Archive - Archive Attender (is the software it runs)
3. Windows 2008 Terminal Server (max 5 users)
4. Vcenter Appliance
5. APCNS - Ups shutdown applance

Its a standalone host, not part of a cluster.  There are only 25-35 users on the system

I have also configured the Windows VMs with the ParaVirtual SCSI and allocated 1 Windows Volume per paravirtual controller.

Thanks in Advance,

G

[dmeyner22]

So you have Exchange and Archiving on the same raid set, so yeah you are going to experience high read/writes.  You probably don't need a vCenter appliance since you only have 1 host, you are not leveraging the features vCenter can provide in a Cluster configuration.  Adding cache will reduce the I/O, you can also add an SSD and enable virtual flash read cache on your host for your Exchange server.  Exchange is most likely going to be your biggest culprit.

You sound like you have a small environment and maybe money is an issue, but you should really consider another host in a VSAN configuration or getting shared storage with automated storage tiering.  That would help alleviate your latency issues and give you some redundancy.