Btrfs RAID-10 performance

[Miloslav Hůla]

Thanks for the tips!

Dne 07.09.2020 v 15:24 Scott Q. napsal(a):
> 1. I assume that's a 2U format -24 bays. You only have 1 raid card for 
> all 24 disks ? Granted you only have 16, but usually you should assign 1 
> card per 8 drives. In our standard 2U chassis we have 3 hba's per 8 
> drives. Your backplane should support that.

Exactly. And what's the reason/bottleneck? PCIe or card throughput?

> 2. Add more drives

We can add 2 next drives, and we actually did yesterday, but we keep 
free slots to be able replace drives by double-capacity ones.

> 3. Get a pci nvme ssd card and move the indexes/control/sieve files there.

It complicates current backup and restore a little bit, but I'll 
probably try that.

Thank you,
Milo


> On Monday, 07/09/2020 at 08:16 Miloslav Hůla wrote:
> 
>     Dne 07.09.2020 v 12:43 Sami Ketola napsal(a):
>      >> On 7. Sep 2020, at 12.38, Miloslav Hůla <miloslav.hula at gmail.com
>     <mailto:miloslav.hula at gmail.com>> wrote:
>      >>
>      >> Hello,
>      >>
>      >> I sent this into the Linux Kernel Btrfs mailing list and I got
>     reply: "RAID-1 would be preferable"
>     (https://lore.kernel.org/linux-btrfs/7b364356-7041-7d18-bd77-f60e0e2e2112@lechevalier.se/T/).
>     May I ask you for the comments as from people around the Dovecot?
>      >>
>      >>
>      >> We are using btrfs RAID-10 (/data, 4.7TB) on a physical
>     Supermicro server with Intel(R) Xeon(R) CPU E5-2620 v4 @ 2.10GHz and
>     125GB of RAM. We run 'btrfs scrub start -B -d /data' every Sunday as
>     a cron task. It takes about 50 minutes to finish.
>      >>
>      >> # uname -a
>      >> Linux imap 4.9.0-12-amd64 #1 SMP Debian 4.9.210-1 (2020-01-20)
>     x86_64 GNU/Linux
>      >>
>      >> RAID is a composition of 16 harddrives. Harddrives are connected
>     via AVAGO MegaRAID SAS 9361-8i as a RAID-0 devices. All harddrives
>     are SAS 2.5" 15k drives.
>      >>
>      >> Server serves as a IMAP with Dovecot 2.2.27-3+deb9u6, 4104
>     accounts, Mailbox format, LMTP delivery.
>      >
>      > does "Mailbox format" mean mbox?
>      >
>      > If so, then there is your bottleneck. mbox is the slowest
>     possible mailbox format there is.
>      >
>      > Sami
> 
>     Sorry, no, it is a typo. We are using "Maildir".
> 
>     "doveconf -a" attached
> 
>     Milo