question replacing hard disk in raid5 with differnt rotation speed
we have an owc ThunderBay RAID with four Seagate Archive HDD ST8000AS0002 hard disks. it's configured with SoftRAID as raid 5.
now one of the disks is defect and I need to buy a replacement drive.
seagate doesn't sell archive hdds anymore, their specs were:
SATA 6 Gbit/s
4096 (512E) sector size
128 MB cache
5900 rpm rotation speed
the latest barracuda drives have
256 MB cache
5400 rpm rotation speed
the latest ironwolf drive have
256 MB cache
7200 rpm rotation speed
so the barracuda is slower than our actual drives and the ironwolf is faster.
I would like to know, if it should be now problem to replace the defect one with the ironwolf, even it's faster than the actual drives?
These are SMR drives, which means they get very slow on long writes.
SoftRAID does not care about drive performance. So get what you want.
I assume you are going to eventually replace all 4 drives? If so, maybe get all iron wolf, unless you want the lower power consumption Barracuda's.
The Seagate Archive drives apparently explicitly indicated that they are SMR; see https://blocksandfiles.com/2020/04/15/seagate-2-4-and-8tb-barracuda-and-desktop-hdd-smr/
As well, all current Barracuda drives are SMR except the 3.5" 1TB drive; see https://www.seagate.com/ca/en/internal-hard-drives/cmr-smr-list/ . This differs from the Barracuda Pro, which are all CMR.
The Ironwolf are all CMR.
SMR controllers have to rewrite a track if an adjacent track is being written. They avoid writing adjacent tracks until they are half full; after they are half-full, write performance can go down a fair bit.
many thanks for your detailed information, the question now is, can I mix in a RAID5 with 3 SMR-drives with a CMR-drive?
looks like a tricky problem:
I could buy as replacement a seagate barracuda 8 TB, which uses SMR but has only rotation speed of 5.400 rpm (slower than the archive drives with 5.900 rmp)
or I could buy as replacement a seagate ironwolf 8TB, which has rotation speed of 7.200 rpm but uses CMR.
do you have an opinion, which drive I should buy?
many thanks! ferdinand
I would slowly replace your drives with CMR drives, over time. SoftRAID can work with both, even in the same RAID.
As a data point, I have successfully used RAID0 and RAID5 between drives of fairly different speeds.