Expansion of a RAID5 array - can I just add a disk?

[dan_aka_jack]

I'm planning to build myself a RAID5 array but I'm a little confused about the process of expanding an existing RAID5 array...

Say I build a 3 x 500GB RAID5 array this week which will give me 1TB of storage space. Can I just add another 500GB disk in a few months time and gain 1.5TB of storage? In other words, will the RAID5 array dynamically "grow" when I add the new disk or will I have to delete my existing 3-disk array and re-build a 4-disk array?

I'm planning on using a Highpoint RocketRAID 2300 controller card running on WinXP.

Many thanks,
Jack

 

[matja]

Some can. I don't have experience with that particular card myself, but I've done it on Adaptec, LSI Logic and in Linux software RAID.

Adaptec call it OCE (Online Capacity Expansion) and LSI call it OCE and FlexRAID.

I'd download the manual of the card you're looking to buy and have a look for terms like those.

Some of cheaper cards require you to do the procedure inside the RAID BIOS, having to wait for its completion until you start your OS, the more expensive cards can do it on-the-fly (true OCE) while your OS is hammering the array.

 

[rpstewart]

The RocketRaid cards do support online capacity expansion but it takes a wee while to do because all the data and parity needs to be rewritten. The only problem is that while the array can be resized the partition on it stays the same. If, however, you use a dynamic volume on the array you can extend it within Disk Management once the array has been resized.

 

[dan_aka_jack]

HI guys,

Thanks loads for the very swift replies. I'm always amazed at the speed and quality of replies here on OcUK. Thanks!

Erm - what's a "dynamic volume"? Are there any disadvantages to using a dynamic volume rather than a normal partition?

Also - is the data at risk while the array is being expanded? (i.e. will my data survive even if one of the drive dies during array expansion?) I'm guessing not.

Many thanks,
Jack

 

[rpstewart]

A Dynamic Volume is an extension of the basic disk partition concept, the only disadvantage that I can think of is that if you move the disk(s) to a new machine you need to import the volume as a foreign disk before it can be accessed - takes longer to find Disk Management than to do the import.

There's a decent explaination in the XP Help -

ms-its:C:\WINDOWS\Help\diskmgmt.chm::/dm_dynamic_overview.htm

Your data will be at risk during an OCE operation, I suppose flexibility has its price.

 

[dan_aka_jack]

cool, thanks for the reply.