Do you want BusLogic or LSI Logic? Choose wisely.
I’ve been setting up a new home server to host a few vm’s and noticed along the way the poor performance I was seeing from the server. For an initial rundown of the specs:
Motherboard: Gigabyte GA-P35-DS3L
CPU: Penryn E8200 2.6GHz
Memory: A-DATA 8GB DDR2 800
Storage: LSI SAS3442E
Network: gigE
At this time the RAID configuration I was running was RAID 1E with three WD 750 WD7500AACS hard drives. The mentioned “poor performance” was a combination of the following. Transfer speed from another computer on the network of about 3.5 MB/s from a Vista (64bit) physical machine to Windows XP sp3 32 bit virtual machine, downloading updates for another windows xp virtual machine, while trying to listen to mp3′s from a virtual machine to a physical machine the song’s buffer would cut out and sometimes end the song altogether and move to the next, and sometimes data transfers would stop mid-transfer and simply “complete” without an error but that data did copy or move.
Having spend a fair amount of time troubleshooting hardware and performance issues before for desktops and servers I turned to the usual suspects of CPU, memory, network, hard drives (aka I/O). I cut all activities (moving files, listening to MP3′s, etc) testing one at a time and adding one systematically to see if it was a particular one causing the trouble. I used the very handy ESXi Performance tab within the ‘Infrastructure Client’ to gauge system performance. I/O stood out as the culprit and I chalked it up hard drives I was running, which you may have noticed are Western Digital’s “Green” line. This means that rather than running at a full 7200rpm it stayed mostly at 5200rpm increasing as needed. The benefit here is that it draws a lot less electricity, and I already had them on hand when I built the server and were hoping they would be sufficient.
Having it narrowed down to I/O I turned to the knowledgable VMWare Communities I came across the a thread (a newer thread was made since it was getting so long, accessible here) of people posting specific I/O performance using IOMeter and based on the IOMeter configuration file found there I ran some tests of my own. (These test’s were all performed in Windows XP sp3 32bit, as well as the other IOMeter results later shown)
| Test Name | Total I/O/sec | Total MB/sec | Avg IO Resp ms | Max IO Resp ms | % CPU |
| Max Throughput 100% Read | 1392.61 | 43.52 | 43.99 | 808.31 | 19.51 |
| Real Life – 60% Rand, 65% Read | 113.25 | 0.88 | 528.28 | 1594.38 | 14.10 |
| Max Throughput – 50% Read | 94.96 | 2.97 | 628.82 | 2266.18 | 14.57 |
| Random 8k – 70% Read | 75.55 | 0.59 | 788.23 | 5399.25 | 13.85 |
The numbers above caused my jaw to drop and over the following couple days from then pondering what to do I saw a sale Dell was having on Western Digital “Black” hard drives model . Unlike the Green drives these were made with performance in mind. So I ordered up four of them in 1TB with the intention of configuring them up in RAID 10.
Days pass, I get them in, install them, and set them up in RAID 10. In short order I move the same virtual machines to the new datastore and re-run the same IOMeter test to see the results.
| Test Name | Total I/O/sec | Total MB/sec | Avg IO Resp ms | Max IO Resp ms | % CPU |
| Max Throughput 100% Read | 743.40 | 23.23 | 81.7536 | 495.4186 | 15.03 |
| Real Life – 60% Rand, 65% Read | 148.70 | 1.16 | 401.6210 | 2453.4196 | 13.60 |
| Max Throughput – 50% Read | 125.92 | 3.94 | 475.4601 | 1919.5262 | 13.35 |
| Random 8k – 70% Read | 139.83 | 1.09 | 426.9836 | 2789.4462 | 14.05 |
I was astounded, and rather frustrated at this point.
I turned again to the VMWare Community and saw a couple scattered posts about choosing different ‘SCSI Controller Type’ based on the SCSI/RAID card that’s being used. Checking the type in use I see it’s ‘BusLogic’, which I thought was odd since I’m most certainly using an LSI card. The BusLogic setting is what ESXi created for me when setting up a new virtual machine and not something I was prompted to choose. I proceed to change the SCSI Controller Type from ‘BusLogic’ to ‘LSI Logic’ for the previous configured vm but that resulted in nothing but blue screens with instantaneous rebooting once the blue screen was reached. I conceded to creating a new vm and reinstalling Windows XP sp3, with changing the SCSI Controller Type after the wizard of creating a new virtual machine and the results were…
| Test Name | Total I/O/sec | Total MB/sec | Avg IO Resp ms | Max IO Resp ms | % CPU |
| Max Throughput 100% Read | 12392.23 | 387.26 | 4.598 | 291.9839 | 36.33 |
| Real Life – 60% Rand, 65% Read | 358.07 | 2.8 | 162.0115 | 1115.5989 | 9.73 |
| Max Throughput – 50% Read | 243.33 | 7.60 | 240.3390 | 2361.3908 | 8.71 |
| Random 8k – 70% Read | 390.20 | 3.05 | 147.6751 | 927.4924 | 9.53 |
Certainly better than what I was getting previously and I don’t have the same issue’s mentioned previously. I am not thrilled by any stretch about the write performance and the read transfer doesn’t hit that high outside of the test. I don’t have a number offhand but its not even close to that, its under 10MB/s. At this point I’m not sure right now what the next step may be. Is it a limitation in ESXi since it is the free version? Is it the RAID card? Physical to Virtual data transfers (Vista to XP) cap’s out at about 6 MB/s with a more consistent speed of about 4.35. Certainly nothing to get excited over but it is stable and I’m not having the same issues.
The point of this is if you are deciding between BusLogic vs LSI Logic there is most certainly a difference and one should test prior to adding virtual machine’s to make sure the best is chosen.
Your time and comments are appreciated. I’m finding the same issue with disk performace on a production server. All the other production servers I have setup or converted are 64bit ESXi 4.1 boxes and this 3.5 box that doesn’t have virtualization hardware is the first box I have encounter with such severly bad disk I/O performance. In my case I have a HP Proliant DL380 with 3 x SCSI U320 HDD’s and see approx from 8 – 14MB’s+ max when copying VM’s from one box to another, I was shocked.