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Hard drive upgrade strategy

Mark Farey
Occasional Contributor

Hard drive upgrade strategy

I have a Prioliant ML370 with a Smart Array 5300 Controller. There are six physical hard drives; 2 x 18.2G RAID1 and 4 x 36.4G RAID 5 plus a Spare.

I'm planning to replace the 36.4G drives with new 146.8G drives and then redeploy two of the 36.4G drives in place of the 18.2G drives.

I will replace each of the 36.4G drives, one-at-a-time, allowing each one time to automatically reconfigure so that I end up with the same logical drive, which I will then expand using ACU to the new maximum size.

I then plan to take two of the surplus 36.4G drives and replace the two 18.2G drives by again plugging them in one-at-a-time and allowing them to reconfigure. I will then expand the two logical drives therein, using ACU, to the new maximum size.

My questions are:

- Is this a good strategy overall?
- How long will it take, very approximately?
- Can I enlarge the logical drives with the ACU, or will I need a third-party tool, like Partition Magic?
- Will moving a used 36.4G drive into the RAID 1 array, in place of one of the 18.2G drives work. Do I need to reformat it first?

Any comments or advice will be very much appreciated. This is a first time for me!

Regards to all,
Mark.


4 REPLIES
Rajashekar Chintakunta
Honored Contributor

Re: Hard drive upgrade strategy

Hi Mark,

# Is this a good strategy overall?
> Yes it is a good strategy

# How long will it take, very approximately?
>Ideally the time taken for rebuilding RAID is at abt 15 mins per GB.Some of the dependent factors are:
The time required for a rebuild varies considerably, depending on several factors:
* Priority that the rebuild is given over normal I/O operations (this can be changed using ACU from the SMARTStart CD)
* Amount of I/O activity during the rebuild operation.
* Rotational speed of the hard drives,brand, model & age of the drives
* Availability of drive cache.
* Amount of unused capacity on the drives.
* Number of drives in the array

# Can I enlarge the logical drives with the ACU, or will I need a third-party tool, like Partition Magic?
> You might need to use diskpart. For more information check the following forum:
http://forums1.itrc.hp.com/service/forums/questionanswer.do?threadId=1067079

# Will moving a used 36.4G drive into the RAID 1 array, in place of one of the 18.2G drives work. Do I need to reformat it first?
> When the 36.4G disk is removed in Hot Plug it will mark it self bad and could be used to replace the 18.2G. But always recommended is to erase/format the disk and use it again.

Raid 5 rebuild performance in ProLiant:
http://h20000.www2.hp.com/bc/docs/support/SupportManual/c00419664/c00419664.pdf

Regards,
Raj.
Mark Farey
Occasional Contributor

Re: Hard drive upgrade strategy

Raj,

Thanks for the reply.

I've read the "15 minutes a Gig" guideline but I'm not clear what that means. I have an array of four 36.4G drives that give me a logical drive of 69.5G. If I plug in the four 146.8G drives (one at a time) will that take 4 x 69.5 x 15 mins to = 69.5 hrs to complete? Or will it take 4 x 146.8 x 15 mins = 146.8 hrs to complete!

I assume I have to take the system offline while I do this. Maybe I should replace one drive overnight for four nights in a row?

Also, your link to "Raid 5 rebuild performance in ProLiant" is broken. Can you please recitify?

Regards,
Mark.
Rajashekar Chintakunta
Honored Contributor

Re: Hard drive upgrade strategy

Hi Mark,

It should take: 4 x 69.5 x 15 mins to = 69.5 hrs to complete.

Raid 5 rebuild performance in ProLiant:
http://h20000.www2.hp.com/bc/docs/support/SupportManual/c00419664/c00419664.pdf

Regards,
Raj.
Mark Farey
Occasional Contributor

Re: Hard drive upgrade strategy

Hi Raj,

Thanks for the fast response! The link to the Technology Brief worked fine.

A best-case figure there of 50 MB/sec for the rebuild rate would suggest a time of only 20 sec per GB. That's assuming an array of 3 drives and a 64 KB stripe size.

If you look at the figures at the top of page 7 in the paper, you will see a worst case figure of 31.29 MB/sec or about 32 secs per GB, not 15 minutes. That's with no host I/O.

Am I missing something?

Regards,
Mark.