UCS C240 M3L + UCSC RAID SAS 2008M-8i - problem with low write speed

[Lukasz Referda]

Hello everyone!

After many tries of solving problem I would like to ask for help. I have got 6 servers UCS C240 M3L with Cisco UCSC RAID SAS 2008M-8i controllers. My colleagues see problems with write to drives, so they did speed test. In results we have got 20-400MB/s read and 9-22 write speed (CrystalDiskMark), it depend on server, used space and current tasks, but even for less-used server it is definitely too low. We compared results with other servers of similar class and those speeds are even 10x bigger.

Each one has got 4 disks 1TB TOSHIBA MG03SCA100, they are working in RAID 5. All of servers were installed about 1,5 year ago, some of them run only few monhts, but problem appears at all of them. They were configured by one guy, but now we have problems with contact to him, so I hope that you could help me to find what is going on. Probably this test was never done before, but now we have more data and now we start to see the problems. It seems to be some error during configuration of RAIDs.

Till now I tried install new drivers, defrag, reduce unusefull processes, antivir - no effects.

Could you tell me what could cause those problems? I'll give any necessary information, but I'm not so proficient in CISCO servers, so please tell me in simple words ;)

I and my colleagues will appreciate any help.

[Kirk J]

Greetings.

Please keep in mind the 2008M controller has no cache, and no BBU/Supercap, so there is no write back caching that normally gives write speeds and latencies a big boost, especially to traditional drives.  In your case the Toshiba drives are 1TB SAS 7.2K RPM LFF.

It is possible to add in a LSI 9271-8i with 1 GB cache/supercap,, which would import the raid groups from the 2008M, and you would see a significant improvement in both read and write through-puts.

Thanks,

Kirk...

[Lukasz Referda]

Hello Kirk

Thank you for answer, now it makes sense... Additional controller is good solution, little difficult for us because we have closed budget for this project, but of course available. My friend put me some suggestion - do you think we can install 32GB SSD swap disk? Will 2008M-8i be able to configure and operate in this way?

Best regards

[Kirk J]

The C220M3L servers were not originally tested/supported with the hot swap 2.5" or 3.5" SSDs.  The specsheet for c220M3S does now have some SSD options., The C220M3LFF specsheet  currently seems to be offline, or have bad link.  Checking to see if there is an updated link on what SSD drives you might be able to use.

The C220M3 servers do have a couple of internal SDcard(flexflash) slots, that get provisioned via the CIMC, storage, flexflash controller menu.  These normally autocreate a fat32 HV partition that was designed to provide boot location to run ESXi from.

I don't know the exact performance specs on the flexflash cards, but would expect those to be somewhat similar to what you would get from those kind of cards in a tablet or camera, probably not an ideal swap file location.

Thanks,

Kirk

[Lukasz Referda]

Hi Kirk

I read about SD cards solution in those days, but I'm not sure is it the best way to go, actually as you said. I didn't found any information if I could use cards like swap disk. Of course I can as fast partition, but even of that I'm affraid about lifetime of cards because of write operations quantity.

In meantime I got information that there is possibility to add some memory to  UCSC RAID SAS 2008M-8i controller, which would work as cache and improve read/write speed. Could you confirm this information? This solution would be probably much cheaper than buying additional RAID controllers with memory.

Best regards