SAS RAID Questions

[Aknosis]

These are both things I should know but alas my hardware knowledge is lacking in this aspect.

I have a RAID 10 Setup of 8 146GB SAS drives (all identical). The drives are segmented into groups of 2 with 4 groups total (1 of those groups being a pair of hot swaps)

The controller is a Sun StorageTek SAS (http://www.sun.com/storage/storage_networking/hba/raid/raid_internal.pdf)

I'm on the verge of filling up the drives and I need to expand, so...

1. Can I add 3 300GB drives (1 as a hotswap) drives to increase capacity or does the entire array fit to the size of the smallest drive?
   • (I don't need tons of free space and adding just 1 pair of 300s would set me free for at least two years)
2. Can I add drives that are 6Gb/s to my controller that supports only 3Gb/s?
   • (If I can buy faster drives now, I should... After enough drives are replaced a new raid card may be warranted)
3. Any suggestions on 2.5 SAS Drives? Looking @ 300GB http://www.seagate.com/www/en-us/products/enterprise-ssd-hdd/savvio-10k/

TIA

 

[LokutusofBorg]

Uh... RAID 10 requires 4 drives minimum per array, so not sure what you mean by you've got them segmented into groups of 2.

If you (are able to) add 300GB drives to that array you'll only be able to use 146GB of each 300GB drive.

SATA3 should be backwards compatible with SATA2.

Are you buying these drives for a server? If so, just go through your hardware vendor and buy their recommended 10k drive.

 

[alaricljs]

That card is an LSI Logic rebadge and it supports array expansion. You just have to follow their docs on expanding the array. I don't know whether it allows for expansion via disk swaps or just adding disks.

 

[Aknosis]

These drives are for a SunFire x4150 to be exact, we got a steal from Sun because they were clearance prices... The seagates I linked are basically the revisions of what is currently in there.

I (think) what I meant by the pairing is that among the 6 drives used we stripe across 3 drives and each of those are mirrored -- I guess I'm just explaining that this is raid 10 and not 0+1

My understanding is I can pull one of the mirrored pairs out and replace with the larger drive and then once the array is rebuilt on that one I can do the same with the other in the mirror.

I'll have to try and decipher the documentation I have, the command line tool while powerful is a bit cryptic in its interface.

 

[Aknosis]

I think this card is actually and Adaptec Rebadge

 

[mv2devnull]

So you have three RAID1 arrays and you have a striped over them?

We could think that as RAID0 of three "disks". The data is striped. Each disk gets equal chunk from the stripe. If one disk would grow, then the chunk on it should grow too, which would lead to unequal sized chunks.

"Online capacity expansion" seems to be the keyword to look for.

RAID 01 could be easier: detaching one "leg" of the mirror, creating new striped volume from larger disks, copying data to it, and then migrating that RAID0 to RAID01 by adding the another leg.


But how about this:
1. Buy a SATA/ESATA/USB drive of at least 500GB.
2. Copy data to that drive.
3. Replace all disks and create new larger volume.
4. Copy data to new volume.

You do want to have a backup anyway.
Your data remains safe and sound in the smaller SAS drives during the operation.
However, some downtime is unavoidable this way. Should be quick compared to online expansion.

 

[alaricljs]

The pdf you linked is to an LSI card. The Oracle/Sun documentation for that card states that array expansion can only be done via adding drives, not replacing.

You'll have to do it mv2devnull's way. Backup, create new, restore.

 

[alaricljs]

BTW - on your original post RE: 3Gbps vs 6Gbps the only reason to upgrade your card to 6Gbps is if you are using port multipliers somewhere in the topology. Since this is an internal card in a x4150 you are NOT using port multipliers so the 6Gbps option is a waste unless you plan on moving the disks into some external array that's using port multipliers and is 6Gbps.

 

[Rubycon]

By all means whichever way you choose to go ALWAYS make an image of your current volume and be 100% sure that you can restore it BEFORE making changes to your configuration. This will save many headaches and grief in case something goes awry.

 

[Aknosis]

Thanks for the insight, I am going to export all of our Xenserver VMs to another hard drive just incase something goes awry.

After much fuss with the boss man it looks like we are moving to RAID 6 with 7 drives and 1 hot spare. This is the cheapest option (since we don't have to buy any new drives) and seems to be almost as fault tolerant as RAID 10 while still allowing us to increase disk space...

I managed to find RAID management software that will allow us to migrate our RAID 10 to RAID 5 and to RAID 6.

My link was but above but the only one I could find at the time, but I can assure you this is an Adaptec card, its funny how much work goes into rebranding not only the hardware but the documentation and software too (seems like a waste of money to me!)