5220 Appliances - Buffer Tuning & Throughput

[SYMAJ]

Does anyone have any experience of tuning throughput on a 5220 Appliance ?

I note that the data buffers are set to 262144 (standard setting) and there are 30 of them.  Are you finding that these require tuning to achieve maximum throughput or are you simply leaving them set to default ?

I have a Virtual Master server at 7504 and a single 5220 acting as a media server attached to both SAN (for VMware integration) and a tape library containing 2 x LTO5 drives.  I am backing up VMware machines using the VMWARE policy type (SAN transport), physical machines using agents over the network and CIFS data using the NDMP policy type.

In addition, I am using AIR to replicate to a similar configuration for DR.

Before I start tuning I thought I would put this out there to discover what everyone else may have already found as best practice......

AJ 

[Mark_Solutions]

Best left as they are I have found though if your tapes have been used elsewhere with a different block size they will need to be relabelled to change them to use the 256kb size

I have also found that a Storage Unit fragment size of 5000MB helps, especially for GRT restore and duplication performance

Also do not enable compression in the pd.conf on the appliance  as that reduces performance

There are some performance guides out there for 7.5 de-dupe which do apply to the appliances as well but in general they are best left alone

One piunt though .. if it has not come as a 2.5 version unit then try and get a 2.5 USB and rebuild it from the USB rather than patch it (if possible)

Hope this helps

[SYMAJ]

Thanks for the input.

Appliances came at 2.5 so all good there - considering the 251b update in the near/far future, depending on feedback.

Does disabling compression on the appliance have a major side effect on space utilisation ?  By default the appliances had the compression set to enabled (CLISH, SETTINGS/DEDUPLICATION/COMPRESSION).  Can this be simply re-enabled if required ?

After changing nothing, when duplicating to 'brand new' LTO5 tapes I notice that it uses 30 data buffers with a buffer ssize of 65536.  Any ideas here ??

AJ. 

[Nicolai]

In general  when writing to tape you should use a 256K block size and at least 128 buffers.

Just demonstrate what difference it does it did this test when LTO3 has hot. 

Before tuning: 19MB/sec (default values)

Second tuning attempt: 49MB/sec (using 128K block size, 64 buffers)

Final result: 129MB/sec  (using 128K block size and 256 buffers)

Since it's a LOT3 drive have a native transfer rate of 80MB/sec any further tuning attempt are meaningless.

[Mark_Solutions · Accepted solution]

You can change the buffer sizes from the CLISH (or drop into the O/S and add the usual touch files)

I would set the SIZE_DATA_BUFFERS to 256kb (262144) but when doing this also set the SIZE_DATA_BUFFERS_DISK to what ever value you want (1048576 usually works OK), otherwise they will both use this setting - same goes for the number of buffers.

You can enable and disable compression when ever you like - but I would start with it disabled and see how it goes.

The 2.5.1b update is identical to the 2.5.1 update - only the installer has changed so you can take into account any feedback that has already been provided from that one so far.

Hope this helps

[SYMAJ]

Thanks for the input.  I have set the buffers through the clish - and a SHOW command verifies they have been updated.

In two minds about rolling in the 251(b) update yet.  I understand that there is no code difference between this and the original whcih was withdrawn - only changes being in the installer code.  My only drivers in putting this in sooner rather than later would be the updated NDMP stream handler for EMC VNX and the VMware SAN restore update.  Any thoughts..... 

AJ

[Mark_Solutions]

If you are doing NDMP backups then I would go for it - it is supposed to help a lot

The issues I have seen with the updates have all been ones upgraded from 2.0.3 to 2.5 to 2.5.1

As yours came at 2.5 then I think you will probably be OK - your choice of course!

[SYMAJ]

One last point - we covered increasing the size of the disk data buffers, but what about number of buffers for regular and disk ?  Any recommendations....

AJ

[Mark_Solutions]

All defaults are to use 30 buffers - I tend to use 32 or 64

As these things have plenty of RAM then try 64 and see how it goes