Howto Benchmark Disk I/O for SAN, RAID, Virtual Disk?

[Peroxyde]

Hi,

We have a slow performance issue where sequential write is very slow in a HyperV VM. Roughly 4x slower than a file transfer from physical to physical disks. In order to narrow down the cause, I would like to make some Disk I/O comparison in sequential and random R/W between various disk subsystems: SAN unit, RAID 0+1, and virtualized disks inside the HyperV VM.

Can you please recommend a tool suitable for this task? The environment is Windows Server 2008 R2 64 bits.

Thanks in advance for any help.

 

[Emulex]

tell us your hardware setup bro.

http://www.mssqltips.com/sqlservertip/2127/benchmarking-sql-server-io-with-sqlio/

SQLIO works.

iometer, as ssd, (any of the modern ssd benchmarks for simple layouts).

1. AD servers disable write back caching, never run anything on an AD server
2. Make sure you have write back caching enabled on your drives and raid controller. Raid controllers use Battery or FLASH backed write cache. IE. DL380p P420 with 2GB Flash Back write cache with super capacitor. Tunable - 25% read/75% write for raid-10, 50%/50% for raid-5/6, stripe size all matters.
3. Controller drivers in VM, not all drivers are the same, for example in esxi the vmxnet3 driver is by default set to run on core 0 only (ESXi 4) but in hyper-v3 their driver defaults to use all vcpu cores. Same with disk drivers, check that they are dispatching across all cpu's to avoid bottleneck.

Vm's are a pita because you have buffers in the VM, buffers in the host, and buffers to the storage (Disk queue) that all have to play nice or one vm might eat up all the i/o and choke the other vm's.

Tell us your setup hardware wise and vm wise all the details and perhaps we can help you nail the ah heck down.

RAID-0+1 is not really used anywhere, HP uses RAID 1+0 for mirroring on two or more disks - both called raid-10.

Hp disabled the drive write cache for SATA disks by default, enable it if you trust your drives. This is not the battery/flash back write cache, but the drive cache itself. SAS drives for instance are enabled by default.

All the gory details dude. we'll help