| 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
| ||
|
Message-ID: <200607152320_MC3-1-C51B-11C9@compuserve.com> Date: Sat, 15 Jul 2006 23:17:35 -0400 From: Chuck Ebbert <76306.1226@...puserve.com> To: "Jonathan Baccash" <jbaccash@...il.com> Cc: linux-kernel <linux-kernel@...r.kernel.org> Subject: Re: raid io requests not parallel? In-Reply-To: <e0e4cb3e0607151704o479371afpc9332a08fb84ba09@...l.gmail.com> On Sat, 15 Jul 2006 17:04:57 -0700, Jonathan Baccash wrote: > As expected, the multi-threaded reads are 2x as fast as single-threaded > reads. But I would have expected (assuming the write to both disks can > occur in parallel) that the random writes are about the same speed (10 > seconds) as the single-threaded random reads, for both the > single-threaded and multi-threaded write cases. The fact that the > multi-threaded reads were > twice as fast indicates to me that read requests can occur in parallel. > > So.... why doesn't the raid issue the writes in parallel? Thanks in > advance for any help. But it does issue writes in parallel. The problem is in the way RAID1 works. When you do a read from the RAID1, it issues one read request to one of the underlying disks. When you do a write, it issues one write request to _each_ of the underlying disks. So with two disks in the mirror set, every write issued by your program causes two disk writes. -- Chuck "You can't read a newspaper if you can't read." --George W. Bush - 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/
Powered by blists - more mailing lists