IBM ServerRAID Performance

[terrywilson]

I am just doing some testing on x345 boxes with ServerRAID 5i controllers. New builds of W2k, server, firmware is updated to the latest, as are drivers.

Now, I have noticed that when I created a new volume under Disk Management in windows, I made a 300G partition and formatted it; the format was instant - not what I had expeted at all. However, the lights on all of the drives have been going nuts - if I open ServerRAID, it is sitting with a progress bar down the bottom - Synchronizing: Controller1, logical drive 1, which is going up very slowly.
I am guessing my request has ben queued somewhere and while the os saw it as being instant, the work itself is still being carried out on the raid adaptor?
Is there a way to determine how busy the raid adaptor is, and monitoring what it is doing? Thanks.

 

[JG5]

I'm not all that familiar with IBM specific RAID controllers, but the drive will immediately show up as formatted once you create it. The OS makes the drive available, but the formatting is happening in the background. I found this out when I was installing and formatting a SATA array for my backups. I created 4 1+ TB volumes and formatted them. They were immediately available to Windows, but it actually took several hours for the format to complete.

 

[technome]

Many raid adapters initialize in the background after an array set is first setup, nothing to do with the Windows format. The background initialization will allow you to install the OS and software. I prefer to let the initialization complete before the Os install but with very large arrays this may not be practical. One bad feature of background init. is it will restart the entire initialization if the server is rebooted before it completes, no problem to the installation but during the process the server performance is degraded considerably.

 

[scsiraid]

ServeRAID makes a RAID 5 logical drives available immedietly and performs synchronization in the background. It can take quite a while for RAID 5 sync to complete. While sync is going on, any write into areas that havent been sync'd yet are going to require all drives to be read so the correct parity can be generated and stored in the parity stripe. This generates more IO than you would normally expect to see.

 

[scsiraid]

Technome... ServeRAID doesnt restart the entire sync operation if power cycled. It keeps a checkpoint in NVRAM so it can restart from approximately where it left off.

 

[terrywilson]

Am I correct in assuming that the rebuild rate on the controller would dicatate the initial performance hit? This is part of a DR exercise where we want to be able to know how long it will take to create a server from scratch; however, having noticed how unresponsive it was following the initial windows install it appears that the array build takes quite a while; we can see a progress bar with the actual initialising the array job under ServerRAID but I need to know if changing the rebuild rate to low will give us better performance for the initial build while we are configuring and installing the additional programs etc. Thanks.