Chapter 21 : Solutions to Disk Problems

Solutions to Disk Problems

Defrag your disks

Once disks fill to 70% capacity they slow down dramatically. The other side of the coin is that a defrag can cut queues in half. Incidentally, I am always on the lookout for such cost-nothing solutions.

Starting with Windows 2000, Microsoft have licensed part of Diskkeeper. What you can do is defrag a server drive-by-drive. What you cannot do is schedule a defrag for the middle of the night, neither can you select multiple drives for defragging. So the answer is to get a good third party defragger like Diskkeeper's full product.

Faster disks

The logical solution is to buy faster disks. Go to your existing disk manufactures site and compare their figures with the data you collect for:

PhysicalDisk: Disk Read Byte /sec

PhysicalDisk: Writes /sec

Other Servers

Another cost-nothing solution would be to move the files or database to another server. Alternatively you could use the load-balancing properties of DFS.

Disk Striping

This would be my least favoured option. Technically it is a neat idea, to stripe data across two or more disks. The principle reminds of school days when I had to write out, 'I must not run across the school grass' 500 times. To speed up the process I wrote my lines with 3 pens at once. The multiple disk controllers, like my pens, write simultaneously across three disks. The reason I am wary of this method is that there is no redundancy, if any one disk fails you would lose all the data. Of course you could use hardware RAID 5, 10 or 20 which would protect your data against one disk failing.

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Diskperf -y and Performance Monitor

Diskperf's overhead is very small and my advice is to leave it turned on. Another hint that this is the correct approach is that Windows 2003 has diskperf on by default. If you have Windows 2000 and you do not set diskperf -y then you are storing up a problem for when you ever do need to measure disk performance. The problem is that setting diskperf needs a reboot and it would be most inconvenient when you are keen to get on with the troubleshooting.

Perfmon situation 2000 and 2003

DISKPERF [-Y[D|V] | -N[D|V]] [\\computername]

-Y Sets the system to start all disk performance counters when the system is restarted.

-YD Enables the disk performance counters for physical drives. when the system is restarted.
-YV Enables the disk performance counters for logical drives or storage volumes when the system is restarted.
-N Sets the system to disable all disk performance counters when the system is restarted.

-ND Disables the disk performance counters for physical drives.
-NV Disables the disk performance counters for logical drives.
\\computername Is the name of the computer you want to see or set disk performance counter use.
The computer must be a Windows 2000 system.

NOTE: Disk performance counters are permanently enabled on for
systems beyond Windows 2000.

Summary for Disk Monitoring

Be aware that with Windows Server Disk monitoring there are both physical and logical disk counters. Disk activity could mask memory shortage, so always monitor the 'big 4' counters, Memory, Processor, Disk and Network.