Cannot combine 512b and 4KB SAS disks into raid 5 with Perc H330

Martin Andel
Martin Andel used Ask the Experts™
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I have a PERC H330 card and would like to build an 18TB raid 5 array out of four HGST 6TB SAS disks. Two disks are 512b, 6Gb/s and the other two 4KB, 12Gb/s.

For some reason though I cannot add them into the same array. They work in separate raid 1 arrays but that isn't what I want.

Is it perhaps the case of an old firmware version on the PERC card (4.290.01-8335) or I simply cannot combine the two types of disks together?
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Top Expert 2014
Commented:
kevinhsiehNetwork Engineer

Commented:
I see three issues.

1. Mixing drive sector sizes.
2. RAID 5 using large HDD
3. RAID 5 on PERC H330

The PERC H330 doesn't have any cache, so it has really, really poor performance under any parity RAID system.

Depending on the UBR rate of those disks, RAID 5 isn't recommended under any controller due to the very real possibility that you can't rebuild from a single drive failure.

For a 4 drive system I would only use RAID 10. For more than 4 large hard drives. I would use RAID 10 or 6, depending on capacity and performance requirements.
Martin AndelSenior IT Analyst

Author

Commented:
Thanks guys! I used the "sg_format"command (sg3_utils package on installed Ubuntu live memory stick) to reformat the 4KB disks to the logical 512b sector size and also bit the bullet and set the RAID 10 array up instead of RAID 5. That lost me 6TB of available space but hopefully in favour of reliability and performance.

BTW, when formatting with sg_format command, you have to use the "--six" argument if you receive errors like "Illegal request sense key"

The whole command I used to reformat to 512b sector size was therefore:

sg3>sg_format --format --size=512 --six -v sda1
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Top Expert 2014

Commented:
Might be a good idea to write "512e" on the disks lest it baffle someone later who goes by the part number on it.

As a matter of interest how long did sg_format take? I would guess very quick as it's just a logical operation,
Martin AndelSenior IT Analyst

Author

Commented:
Might be a good idea to write "512e" on the disks

Good thinking, I might do that! :)

how long did sg_format take?

On the contrary this was a rather lenghty process. Somenwhere in the region of 8 to 10 hours on two disks being done simultaneously.
Top Expert 2014

Commented:
Of course, it doesn't do fast format unless you set --ffmt=1 or 2.
Martin AndelSenior IT Analyst

Author

Commented:
Ha! I did not know that :) Doesn't matter. It got the job done regardless. Thanks again for your help!

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