Date: Mon, 12 Mar 2001 18:47:55 -0600 From: David Kelly <dkelly@hiwaay.net> To: Alfred Perlstein <bright@wintelcom.net> Cc: Kevin Oberman <oberman@es.net>, Soren Schmidt <sos@freebsd.dk>, mobile@FreeBSD.ORG, stable@FreeBSD.ORG Subject: Re: Disk I/O problem in 4.3-BETA Message-ID: <200103130047.f2D0lte06674@grumpy.dyndns.org> In-Reply-To: Message from Alfred Perlstein <bright@wintelcom.net> of "Mon, 12 Mar 2001 14:06:36 PST." <20010312140636.A18351@fw.wintelcom.net>
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Alfred Perlstein writes: > * Kevin Oberman <oberman@es.net> [010312 13:46] wrote: > > > > How serious is the possible corruption issue, anyway. The loss in > > performance is pretty drastic although it may be that dd is an > > especially bad case, but I really don't like to corrupt my disks, > > either. > > If basically running with blind write caching turned on is akin to > running your filesystem in async mode. This is because write > caching gives the drive license to lie about completing a write, > the various ordering of writes are effectively bypassed. If you > crash without these dependancies actually written to the disk, when > you come back up you have a good chance of losing large portions > of your filesystem. If I'm not mistaken when write caching is disabled the ATA drive does not return from the write command until the data is on disc? And that ATA drives can not overlap or queue pending commands so the pending read/writes have to queue in the kernel? Is tagged queuing the solution or is that something else? The FreeBSD kernel has a built in daemon called syncer. It sounds like a natural place to periodically issue a sync command to such storage devices. Assuming such a command exists. My "purchased because they threw in a USB Zip-100 and ATA-100 PCI card" 45G Maxtor is awfully impressive. 32000 blocks of 128k staring 8G from the begining of the disk resulted in over 30MB/sec according to dd. I'm stunned. Kernel from mid-Feb. -- David Kelly N4HHE, dkelly@hiwaay.net ===================================================================== The human mind ordinarily operates at only ten percent of its capacity -- the rest is overhead for the operating system. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-mobile" in the body of the message
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