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RAID

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Tom Melvin
Occasional Contributor

RAID

It's been suggested that we do a RAID 1+0 for the OS, and 5 for data, using a spare for each. It's on a DL380/4. Any suggestions? Is it done via the SmartArray tool, or the OS?
8 REPLIES
Vijay_44
Honored Contributor
Solution

Re: RAID


Typically you want to boot off the SmartStart CD that come with the server, and run the Array Configuration Utility. The ACU will allow you to create the array and logical driver. You could create Array A with your os logical drive and Array B with your data logical drive. Depending on the number of driver you have, you can have a separate spare for array of one spare HDD for both arrays.
There’s your problem!!! This thing is set to EVIL!
Ivan Ferreira
Honored Contributor

Re: RAID

RAID configurations are very dependent of what you need mostly, cost, availability or performance.

You don't need a 1+0 for the operating system, you can use a RAID 1 only.

A spare is always good idea.

For data, if you want maximum availability and performance, choose 0+1, but at the highest cost.

If you want a balance between performance and availability, choose RAID 5.

For the OS RAID, you must do the configuration from smart start (ACU). After the OS installation, you can run ACU from the smart start or the operating system.

You can use the SmartArray tool only if you have a hardware RAID. You should have one.
Por que hacerlo dificil si es posible hacerlo facil? - Why do it the hard way, when you can do it the easy way?
Colin_29
Trusted Contributor

Re: RAID

Tom,

This is really quite an open ended question. RAID is a trade off between cost, fault tolerance and performance. It depends what you are intending to use the server for. There are loads of white papers but if you have a look at this one you will find it contains most of what you need to know (and lots more than you need). http://h20000.www2.hp.com/bc/docs/support/SupportManual/c00502620/c00502620.pdf

In a nut shell:
RAID 0 gives the best performance and is the most cost effective but gives you no fault tolerance
RAID 1 gives the best performance with fault tolerance but is the highest cost (except RAID 1+0 which is way OTT for most installations)
RAID 5 is normally the best compromise for most installations.

You will often need to mix the RAID levels on installation to get the best performance. This is often the case with anything to do with databases such as SQL-Server or Exchange. where you may have two RAID 0 sets and one RAID 5.

A good generic link is http://h18004.www1.hp.com/products/servers/technology/whitepapers/index.html Have a read and if you have more specific questions then post then back.

Colin
Colin_29
Trusted Contributor

Re: RAID

Forgot to mention: If performance is an issue you should also be looking at the model of array controller that you are intending to use and the size a speed of the disk drives.
Colin_29
Trusted Contributor

Re: RAID

And to pick up on your last point, you should be using hardware RAID. If you utilise software RAID from the OS you may as well be using an elastic band driven server. IMHO.
Shameer.V.A
Respected Contributor

Re: RAID

Hi TOM,

1. " It's been suggested that we do a RAID 1+0 for the OS, and 5 for data, using a spare for each. It's on a DL380/4. Any suggestions"

You can use the smartarray CD of hardware RAID Controller, which was supplied with your server for configuring the server.

If your controller is having more than one channel, then it is recommended to put both array on seperate channels, otherwise will cause a very big performance bottleneck for your operating system as you are configuring O S as RAID 1 & the data part as RAID5 ( RAID 5 will consume your RAID processor and memory resources for the parity generation)

It's not must to spare individual hotspare disks for both arrays, you can have a single global hotspare for both the array. As soon as 1 disk on either array fail, global hot spare will do an auto include & start rebuilding ( incase of RAID5) or copy ( incase of a RAID 1).

But you should have the higher capacity disk to be used as global hot spare ( eg. if your OS - RAID1 is having 2* 36 Gb & DATA -RAID5 is having 5* 146GB, then you have to use a 146GB as global hotspare.

2. "Is it done via the SmartArray tool, or the OS?"

You should create the RAID1 volume before installing the operating system. You can configure the RAID5 before or after installation of O S.

I hope this will help you..


Shameer
.... See invisible, feel intangible and achieve impossible as everything is possible ....
Shameer.V.A
Respected Contributor

Re: RAID

Hi Tom,
If you are not purchased the array controller, then buy one which is having atleast 2 channels & 128MB cache ( with battery backup if possible, so that we can configure write back policy for RAID5, which will greatly boost system performance-by generating & writing the parity later).

RAID1 + RAID5 through software ( O S feature without hardware) is not recommended, as it will consume your CPU & memory just for disk I/O activities and your actual server application will not get the resources.

shameer
.... See invisible, feel intangible and achieve impossible as everything is possible ....
Colin_29
Trusted Contributor

Re: RAID

With regard to a dual channel Array controller; the system can be operated in single channel or dual channel (2/4 split). SCSI configuration kit (364471-B21) is required for dual channel configurations.

The DL380G4 only has capacity for six drives so if you do go to a dual configuration, you will only be able to configure the RAID 5 array with an on line spare.

IMO you should be monitoring the system and with only three drives in the array, the chance of two drives failing are fairly remote. The on line spare is of more use if you have a large number of disks in your array, in which case you are more likely to use ADG (RAID 6).