Re: Disk I/O slowness

[Casey Deccio <casey@deccio.net>]

> On Jul 30, 2026, at 9:32 AM, Andy Smith <andy@strugglers.net> wrote:
> 
> On Thu, Jul 30, 2026 at 07:17:01AM -0600, Casey Deccio wrote:
>> Seagate BarraCuda 5TB Internal Hard Drive HDD – 2.5 Inch SATA 6Gb/s 5400 RPM 128MB
> 
> Almost all high capacity 2.5" SATA drives are SMR (shingled magnetic
> recording) and are really intended for use in laptops, not for serious
> server purposes. I haven't checked this model but I would be very
> surprised if it's not SMR, and the 5.4kRPM also suggests not for server
> use.
> 
> SMR drives have a write cache and after this write cache is filled, the
> write performance is absolutely terrible. A lot of people find them
> unsuitable for use in RAID arrays (or zfs pools) because even the
> periodic scrub can't complete in a reasonable time period.
> 
> This could easily explain the very low performance under write load
> here. Have you used these models of drive before with a better
> performance outcome?
> 
> Consumer-level SATA SSDs will definitely perform better though the cost
> will be eye-watering (in comparison) for 3x ~4TB or 3x ~8TB. This is an
> issue I have struggled with myself - very very hard to find decently
> performing 2.5" SATA drives.


Thanks for the info.  For this system I did optimize for cost, understanding that there would be some tradeoffs with regard to performance.  I didn't suspect that these issues were related to the drives because I have another setup using the same drives, and it doesn't have this same issue.  To be clear, it has these same drives and it is using a RAID5, but it's on a different motherboard using a MegaRAID controller with hardware RAID.

Thanks,
Casey