Advantage of software RAID in rx2660

[joseph51]

Hi

Can some one please tell me what is the advantage of using software raid on rx2660 than Hardware RAID

[Torsten.]

IMHO none.

Change a LVM mirrored SAS disk with 11.31 running and you will agree ... ;-)

You will prefer hardware mirrors then ...

[S_Logan]

Hi,

Software RAID  vs Hardware RAID:

Benefits and drawbacks of “pure,”Operating System Software RAID:

• Low cost: No extra charge for the RAID functionality, as it is built into the OS. The only cost is the additional disk drives.

• Unprotected at boot (cannot manage or protect data at boot): Drive failure or corrupted data during boot and before the RAID software become active leads to an inoperable system.

• Additional performance load on server: System performance is impacted by the RAID application. The more drives involved and the more complex the RAID system is (e.g. involving parity on a RAID 5), the more impact on the overall performance. This solution is better suited for simple RAID 0, 1, 10 scenarios.

• Limited operating system migration: RAID functionality might be limited to the current OS. There is no way to migrate the array to other OSes or other versions of the same OS, if not all versions of the OS support RAID functionality).

• Vulnerable to viruses: Because RAID is running as an application on the computer system, viruses and other harmful software could impact RAID functionality.

• Data integrity issues due to system crashes: Software or hardware problems on the server can impact data consistency and integrity.
•  
• No write-back cache: Software RAID runs only in writethrough mode, but hardware RAID can run in write-back mode if it has a battery, adding another level of data protection.Write-back mode significantly enhances the write performance of a RAID array. There is no way to add a battery for software RAID.

More Infromation:

http://www.dataonstorage.com/technology/102-hardware-raid-vs-software-raid.html

HTH

Surendar

How to assign KUDOS! Click the STAR!

[S_Logan]

Hi Joseph,

Please check this PDF link also:

http://www.adaptec.com/nr/rdonlyres/14b2fd84-f7a0-4ac5-a07a-214123ea3dd6/0/4423_sw_hwraid_10.pdf

HTH

Surendar

How to assign KUDOS! Click the STAR!

[Robert_Jewell]

@Surendar - your comments may apply in a generic form, but in regards to HP-UX they dont specifically apply:

> Low cost: No extra charge for the RAID functionality, as it is built into the OS. The only cost is the additional disk drives.

LVM mirroring, Veritas VM, etc are licensed and the only means to acheive software RAID 1, 5, etc on HP-UX.

> Unprotected at boot (cannot manage or protect data at boot): Drive failure or corrupted data during boot and before the RAID software become active leads to an inoperable system.

LVM is not an add on product.  Mirroring is established at the LV level, so protection starts as soon as the VG is activated.

> Additional performance load on server: System performance is impacted by the RAID application..

LVM again is not an application.  its a subsystem of the kernel so there is no performance impact (other than the general write performance to multiple drives).

I only comment to point out the obvious perhaps.

-Bob

[Torsten.]

The rx2660 has 2 options: the default SAS chip or a P400 smartarray controller.

The SAS chip can either present all disks directly or you can create 2 pairs of hardware mirrored disks + hotspare. The P400 always works with logical drives (RAID0,1 or 5). As said, a hardware RAID makes a disk replacement very easy, compared to about 10 different commands you need to run when replacing a LVM mirrored disk. On the other hand you can easily split or remove a mirror with LVM, but this is usually never needed.

So I would always recommend to use the hardware RAID.

[binu_mathew]

Thanks to all

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@joseph51 wrote:

Hi

Can some one please tell me what is the advantage of using software raid on rx2660 than Hardware RAID

---

[binu_mathew]

Hi Torsten ...

Thank you for the good reply .. .

Let me ask one more doubt ,

I have a rx6600 with 4 disk .  Can I create a HW raid 1 with 2 disk and again another HW raid 1 with another two disk

Because we are planning two disk for OS and other two disk for data,

So which is the best solution .

HW RAID 1 for OS disk and HW raid 1 for data disk

or

HW RAID 1 for OS and mirroring for data disk

[Torsten.]

Even with the default SAS controller chip you can create 2 pairs of hardware mirrored disks.

IMHO this is the way to go.

The procedure to create the RAID depend on the controller you have (smartarray P400 controller vs. LSI SAS chip).