Disk defrag?

[matty-ct]

Hi all,

Any comment regarding disk defragmentation tips? I'd like to install server defrag software. Should live Starwind iscsi targets be included in defrag routines? I'm using Starwind Free in Windows 2008 R2 Enterprise as CSV's so the iSCSI targets are not shown as drives. Any advice would appreciated.

Matt

[Constantin (staff)]

Don`t use defragmentation software on StarWind boxes. It has no sense. What I would recommend - Diskeeper 2011 on Hyper-V box, and nothing more.
But anyway you`ll gonna face with random access to disk all the time when hypervizor going to read\write data from VMs.
So, what is the idea: yes, you can defragment your data and keep it sequential, but when few VMs will access their own data - hypervizor will anyway send requests to random sectors.

[matty-ct]

Thanks for the answer. I wrote my question in a hurry. When CSV's are enabled, the mount point is listed as c:\clusterstorage\volume*. If I install diskeeper or perfectdisk and tell it to defrag c: will it attempt to defrag the CSV's as well? I would think not but it's worth asking. Also, if the Starwind image file is on C: I assume that a defrag would significantly impact iSCSI target performance during that operation.

[Constantin (staff)]

AFAIK Diskeeper is aware about CSV and Hyper-V (Velocity is the name of the product AFAIK).
And yes, it will cause huge load on SAN.

[anton (staff)]

Well... Everything is not that easy. Actually you need to run defrag sequence THREE times on different environments:

1) StarWind images residing server. StarWind uses either flat images or allocated disk space with a huge chunks so defragmentation is minimal and it's impact to performance is close to being missing. But you'd better do it at least a couple of times per year.

2) Hyper-V machine. Hyper-V has absolutely crazy VHD file I/O access pattern (unlike VMware ESX) so VHD files keeping VM content could be extremely fragmented. Especially when you have heavy load, lots of VMs, not that much disk free space and Hyper-V cluster. So run defrag on regular basis here.

3) VM itself. NTFS inside virtual machine (or whatever FS you have created with OS you use) also gets fragmented. So you need to run defrag inside VM just like it would be your physical server. Application and load dependent so you should know your schedule better.

That's it