From mboxrd@z Thu Jan 1 00:00:00 1970 From: Hans Reiser Subject: Re: non volatile ram devices Date: Thu, 05 Dec 2002 01:05:58 +0300 Message-ID: <3DEE7C46.9080203@namesys.com> References: <200212042059.35300.russell@coker.com.au> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: list-help: list-unsubscribe: list-post: Errors-To: flx@namesys.com In-Reply-To: <200212042059.35300.russell@coker.com.au> List-Id: Content-Type: text/plain; charset="us-ascii"; format="flowed" To: Russell Coker Cc: linux-ide-arrays@lists.math.uh.edu, ReiserFS , mikej@umem.com, Edward Shishkin Russell Coker wrote: >I have some servers that are giving inadequate disk performance for Maildir >mail spools. They are running kernel 2.4.19 (2.4.20 upgrade is planned) and >using ReiserFS for everything that's important. > >At this stage it is impossible for me to replace disks, RAID controllers, or >anything else really significant. > >What I am thinking of doing is using a kernel that supports data journalling >which should increase performance, but still probably won't give me enough. >So I am thinking of using an "external journal" (or using software RAID to >put the part of the partition containing the journal on a different device). > >The device containing the journal would be something much faster than physical >media. I have been doing some research on non-volatile memory devices. I >only found one company producing disks that are RAM based with battery >backup, and they seem to start at $10K (too expensive - probably because they >are much larger than I need, I need 128M at most, they provide 2G). I found >many companies selling flash memory, but that only takes a million writes >(that'll last about an hour for the use I plan). I found one company selling >PC-Card devices that have two batterys for backup, but that requires getting >a PCI controller for PC-Card's (something I haven't tried before). > >Does anyone know of an affordable ($1000 or less) device that can survive >unexpected power outages of at least 24 hours duration, can commit a write in >less than 1ms, supports unlimited writes, and connects to a IDE or SCSI bus >(or PCI if there's a suitable Linux driver). > > > The umem.com folks sell a device that we have tested and benchmarked reiserfs on. If I could get Edward to format benchmarks in a way that conveys that information that is relevant to persons reading them, I would post them on our mailing list.... Hans