I have two questions. Is there any reasonable reason why WD-RED HDD in RDM (139MB/s) is much faster than my WD-RED in VMDK (98MB/s)? Not true for my SSD, which is enough fast under VMDK.
madrian@ubuntu:~# #SSD (VMDK)
madrian@ubuntu:~$ sync; dd if=/dev/zero of=tempfile bs=1M count=1024; sync
1024+0 records in
1024+0 records out
1073741824 bytes (1.1 GB, 1.0 GiB) copied, 2.90094 s, 370 MB/s
madrian@ubuntu:~$#VMDK
madrian@ubuntu:~$ cd /media/hdd
madrian@ubuntu:/media/hdd$ sync; dd if=/dev/zero of=tempfile bs=1M count=1024; sync
1024+0 records in
1024+0 records out
1073741824 bytes (1.1 GB, 1.0 GiB) copied, 10.958 s, 98.0 MB/s
madrian@ubuntu:/media/hdd$ #RDM
madrian@ubuntu:/media$ cd backup/
madrian@ubuntu:/media/backup$ sync; dd if=/dev/zero of=tempfile bs=1M count=1024; sync
1024+0 records in
1024+0 records out
1073741824 bytes (1.1 GB, 1.0 GiB) copied, 7.70613 s, 139 MB/s
madrian@ubuntu:/media/backup$
I get same values with fio.
My other question is: what do you recommend for me: I have 2-3 Linux OS installed on my Esxi server/primary hdd is an ssd. On my second WD RED I have not very important data. Currently on this HDD I am using VMDK and today I wanted shrink it's size. As I read it's not possible, only by Converter. Meh, I'll skip this. I am now thinking in RDM because it's easier to maitance I think. In this case I would shrink the main partition and create a new one for other OS. What do you think? Or maybe I am going to start again, format the drive and start with a smaller VMDK? Another possibility is to use (multiple) VMDK for different OSes and use thin provisioning to not use full disk? I can't decide which is the best way for the future (expand/shrink disk freely).