Tag Archives: cache

Using Microsoft’s BranchCache with the Celerra & VNX

We recently moved the data from several of our small offices to being hosted at a central regional data center. In one case, a site that formerly had it’s own Celerra for file access was now accessing NAS through a WAN link.  As expected, access to files was much slower.  After doing some research on how to speed up file access for users at the branch office locations I came across Microsoft’s BranchCache feature.

BranchCache is a WAN bandwidth optimization technology and is available on Windows 7 & 8, Server 2008 R2 and Server 2012. When BrancheCache is enabled, it creates a cache of the content from the file server locally within the branch office. A client from the same network can then access the file very quickly from cache instead of having to download it across the WAN again. It’s a great feature for optimizing local link utilization, increasing the responsiveness of applications, and reducing WAN bandwidth consumption.

BranchCache can operate in either Hosted Cache Mode or Distributed Cache mode. In Hosted Cache mode, there is a Windows server configured to store the cached files. In distributed cache mode (appropriate for smaller sites) local clients in the office keep a copy of the content and make it available to other clients that access the same files.

Once your Windows Administrator has BranchCache configured on a server (or it’s been enabled on the local client PC’s), enabling it on the Celerra/VNX side is very simple. Log in to the CLI and su to gain root credentials. Then type in the following command:

server_cifs server_2 -smbhash -service enable

If you’d like to enable BranchCache auditing so the Windows server administrators can see audit info the Windows event logs, type in this command:

server_cifs server_2 -smbhash -audit enable

After that, you will need to restart the CIFS service on the data mover. Here are the commands to stop and start CIFS:

server_setup server_2 -P cifs -o stop
server_setup server_2 -P cifs -o start

To confirm that BranchCache was successfully enabled, type the following command:

server_cifs server_2 -smbhash -info

The output should look like this:

server_2:
Current smbhash parameters:
—————————
Enabled : Yes
Started : Yes

Finally, To enable hash support on each individual CIFS Share that you want to use for Branch Cache clients, use the command syntax below.  Note that EMC’s “Configuring  Branch Cache” document I link to at the bottom of this post does not contain this next command (major oversight).  It was pulled from page 58 of EMC’s Configuring CIFS Guide.

# server_export <datamover_name> -name <fs_name> -option <netbios_name_of_CIFS_Server>, type=hash /<fs_name>

EMC has a detailed document on how to configure BranchCache, including all the steps you’d need to take to configure the server and PC clients. If you have an EMC support account you can download it here:

https://support.emc.com/docu42265_Configuring-BranchCache-V2-on-VNX.pdf?language=en_US

There is also a lengthy section on BranchCache in EMC’s CIFS Management for VNX guide here:

https://mydocs.emc.com/VNXDocs/CIFS.pdf.

Here is the link to Microsoft’s TechNet guide for BranchCache:

http://technet.microsoft.com/en-us/library/hh831696.aspx.

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Problem with soft media errors on SSD drives and FastCache

4/25/2012 Update:  EMC has released a fix for this issue.  Call your account service representative and say you need to upgrade your NS-960 dart to 6.0.55.300 and flare to 4.30.000.5.524 plus drive firmware upgrade on all SSD drives to TC3Q.

Do you have FastCache enabled on your array?  Keep a close eye on your SP event logs for soft media errors on your SSD drives.  I just noticed over 2000 soft media errors on one of my FastCache enabled arrays, and found a technical advisory from EMC (emc282741) that desribes this as a potentially critical problem.  I just opened a case with EMC for my array to be reviewed for a possible disk replacement.  In the event a second disk drive in the same FastCache RAID group encounters soft media errors before the system automatically retires the first drive a dual faulted RAID Group could occur.  This can result in storage pools going offline and becoming completely inaccessible to the attached hosts.  That’s basically a total SAN outage, not good.

Look for errors like the following in your SP event logs:

“Date Stamp”  “Time Stamp” Bus1 Enc1 Dsk0  820 Soft Media Error [Bad block]

EMC states in emc282741 that enhancements are targeted for Q1 2012 to address SSD media errors and dual hardware faults, but in the meantime, make sure you review the SP logs if you have CLARiiON or VNX arrays that are configured with SSD disk drives or are using FAST Cache.  If any instance of the “Soft Media Error” listed above is associated with any one of the solid state disk drives in your arrays, the array should be upgraded to at least FLARE Release 04.30.000.5.522 (for CX4 Series arrays) or Release 05.31.000.5.509 (for VNX Series arrays) and then start a Proactive Copy (PACO) to a hot spare and replace the drive as soon as possible.

In order to quickly review this on each of my arrays, I wrote the following script to update my intranet site with a report every morning:

naviseccli -h clariion1a getlog >clariion1a.txt
naviseccli -h clariion1b getlog >clariion1b.txt  
cat clariion1a.txt | grep -i ‘soft media’ >clariion1_softmedia_errors.csv
cat clariion1b.txt | grep -i ‘soft media’ >>clariion1_softmedia_errors.csv
./csv2htm.pl -e -T -i /home/scripts/clariion1_softmedia_errors.csv -o /<intranet_web_server>/clariion1_softmedia_errors.html
 

The script dumps the entire SP log from each SP into a text file, greps for only soft media errors in each file, then converts the output to HTML and writes it to my intranet web server.