Comments on: Poor LSI SAS1068E Write Performance with Linux

By: shainmiley

shainmiley — Wed, 15 Feb 2012 17:52:28 +0000

Well if you provide me with a little bit more detail I might be able to offer up some help…however as the article states, turning in the write cache option via the admin tools really has little to no actual impact on the performance that you will receive while using this card.

In fact it maybe the case that it simply says that it is enabled and no actual changes are made hardware or software wise. Anyway let me know if you still need help.

By: oknittel

oknittel — Wed, 15 Feb 2012 16:26:31 +0000

I was following your instructions for the “write cache” of that controller. But I don’t find in that LSI tool the menue point to enable write cache.
Please help me.

By: shainmiley

shainmiley — Thu, 03 Mar 2011 16:41:28 +0000

Well we replaced our LSI cards with the Perc ones without any issues. When you install the new card and create the new virtual disks, the controller will present a popup screen suggesting that you initialize the disks, we had existing data on our servers to I choose NOT to do that, and we have not seen any negative side effects of not doing so.

I do not see any reason why you would see any data loss just because you switch between these two RAID cards.

By: Roy

Roy — Thu, 03 Mar 2011 15:42:08 +0000

We’re having the very same issues and are working on a solution: replacing the controller with the Perc 6I controller.

Do you know if these controllers are exchangeable without losing the data?

By: shainmiley

shainmiley — Thu, 04 Feb 2010 16:16:27 +0000

Well I don’t have any hard benchmarks to show you, however since we were running Promox on these servers we were using a perl script that comes with that distro as our benchmarking tool.

The script is called ‘pveperf’. Here is the output from the command:

Original LSI SAS1068E output:

BUFFERED READS: 115.99 MB/sec
AVERAGE SEEK TIME: 6.58 ms
FSYNCS/SECOND: 272.47

New Dell Perc output:

BUFFERED READS: 101.11 MB/sec
AVERAGE SEEK TIME: 6.33 ms
FSYNCS/SECOND: 2509.68

Clearly the seek time should still be about the same…as should the buffered reads. The major performance gains are seen in terms of the write speed (FSYNCS/SECOND) as there is almost a 10X increasing using this metric.

I can tell you for a fact that if you have an I/O intensive application (Mysql, Oracle, Samba/NFS server with heavy writes) for example…you will see a huge increase in performance….and it is all due to the ability of the controller to cache those writes.

We ended up replacing these LSI cards with Perc ones in 10 to 15 of our Dell PowerEdge servers after this discovery.

By: ur

ur — Thu, 04 Feb 2010 15:31:03 +0000

Hey, I’ve got the same LSI SAS controller and i’m thinking about replacing it with Dell Perc. Can you tell me, how big is the performance boost? Have you got any benchmarks?