linux-kernel - Re: RAID performance / tuning?

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Thu, 2 Apr 2009 12:41:37 -0500 (CDT)
From:	david.hagood@...il.com
To:	"Tiago Freire" <tiago.freire@...il.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: RAID performance / tuning?

> Why is it that software RAID on current systems still gets less
> performance than hardware counterparts?

Part of it can be crappy disk interfaces: I was running software raid with
2 SATA-SIL cards, and would frequently be disk-bound with the CPU still
largely idle.

The cards were incapable of talking to more than one drive at a time. They
didn't support command queuing on the drives.

As a result, the system would set up a stripe, queue up the writes, then
have to wait as each write for EACH DISK in the 7 disk array was carried
out.

On a good hardware RAID controller, the disks can be written in parallel,
and the controller will support command queuing - so disk writes can be
run in parallel, and the writes themselves can be better optimized by the
disks.

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/