Hi all,
I run virtual Windows Server 2008 R2 in VMware ESXi 5.0 from local datastore (8 SAS disks in raid 60) on HP ProLiant DL380 G7 server. When i create virtual disk on the same datastore, attach it to virtual Windows Server 2008 R2 and use it as dedicated backup volume i get great speeds for first full backup, and also every consequent backup. This way full exchange backup of around 500Gb gets backed up in less than 2 hours, which I am very satisfied with. However, my fast local datastore is getting low on space and i wanted to offload backups to cheaper external storage. I took older HP ProLiant ML350 G5 with 6 SATA disks in raid 10 and exported them to ESXi (in first test over NFS, in the second over iSCSI, I'll explain right away) from FreeBSD 9.0.
Now, when i create virtual disk on NFS/iSCSI datastore and attach it to Windows Server 2008 R2 as dedicated backup volume, i noticed that first backup gets done with satisfactory speed for this kind of hardware (around 10Mb/s), and this backs up my domain controller of around 20Gb in 30 minutes. But every consequent backup takes much longer, up to 4 hours for the same amount of data, and disk activity shows no more than 1Mb/s for reads and writes.
I do not think it is disk/controller/network I/O problem, because if i start to copy one file from ESXi host to the same datastore, and the other file from the same datastore to the ESXi host while backup is running, files get copied fast and i see increase in disk read/write activity.
So, could this problem be related to some windows backup specifics? And if so, could i get an advice how to get better speeds for consequent VSS backups of Windows virtual servers to NFS/iSCSI datastores?
Thank you in advance.