Re: [zfs-discuss] Fwd: [OT][X-POST] RAID-6 hw rebuild speed

["rob_mailing_lists&rbabb net" <Ufficio.Qualita@vvinternational.eu>]

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On 2020-12-01 12:34, Linux RAID Mailing List wrote:
> On 01/12/20 09:57, Gandalf Corvotempesta wrote: > Sorry for the OT and
> X-POST but these 2 lists are full of skilled > storage engineer. > For a
> very,very,very,very long time I used 15k SAS 3.5'' disks. A > RAID-6
> hardware (8 disks) took about 20 hours to rebuild. > > Now I've replaced a
> 3.5 disks with a 15k SAS 2.5'' disk. raid is > rebuilding properly, but the
> ETA is less then 1 hours. > > I've moved from a 20 hours rebuild to about
> 50 minutes rebuild, by > just changing one 3.5' disks with a 2.5' > > Is
> this normal ? I'm thinking something strange is happening > Your rebuild
> time is effectively the time it takes to write to the new disk. So I'm
> guessing if you had to wipe and rebuild one of the old disks it would again
> be 20 hours. So what's different about the new disk? Yes I know it's a
> 2.5". But could it be it's SATA-3 as opposed to the old ones being SATA-2?
> There's a whole bunch of things it could be. But my money's on it having a
> bigger cache. The ETA is based on how fast it can read from the existing
> array and the rebuild hasn't yet filled the cache. Once that fills up and
> the disk write speed kicks in, the ETA will start climbing fast as the
> write speed starts dominating the ETA. That said, it'll probably be faster
> than the old 20hrs, but I don't know by how much. Cheers, Wol
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