Date: Wed, 8 Jan 2020 10:51:36 +0100 From: Gary Jennejohn <gljennjohn@gmail.com> To: Rick Macklem <rmacklem@uoguelph.ca> Cc: Hans Petter Selasky <hps@selasky.org>, Wojciech Puchar <wojtek@puchar.net>, "freebsd-hackers@freebsd.org" <freebsd-hackers@freebsd.org> Subject: Re: maximum MAXBSIZE Message-ID: <20200108105136.0d54ebce@ernst.home> In-Reply-To: <YQBPR0101MB1427EEDE94AA6E34B49C3C09DD3F0@YQBPR0101MB1427.CANPRD01.PROD.OUTLOOK.COM> References: <alpine.BSF.2.20.2001072210410.21107@puchar.net> <d79078c4-f1cb-93b9-ee6e-f689936c1e01@selasky.org> <YQBPR0101MB1427EEDE94AA6E34B49C3C09DD3F0@YQBPR0101MB1427.CANPRD01.PROD.OUTLOOK.COM>
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On Tue, 7 Jan 2020 22:47:54 +0000 Rick Macklem <rmacklem@uoguelph.ca> wrote: > Hans Petter Selasky wrote: > >On 2020-01-07 22:12, Wojciech Puchar wrote: > >> default MAXBSIZE is 128kB. badly low for todays magnetic disks. > >> > >> i have it set to 2MB on all computers that have magnetic disks. Great > >> improvement with large files. especially when more than one are > >> read/wrote in parallel. And no problems experienced > >> > >> But for optimal performance MAXBSIZE should be transfered in few times > >> longer than average seek time. todays disk do 200-250MB/s so 2MB is > >> transfered below 10ms. > >> > >> 8-16MB seems like good choice. is there any reason not to set it that high? > > > >Old disk may not support it, especially USB 1.0/2.0 disks. > I also thought it was limited to MAXPHYS, but maybe I'm only thinking of the NFS > specific case? > There's a comment in param.h that it should not exceed MAXPHYS to be on the safe side. How old that comment is I can't say and that may not be the case today. MAXBSIZE is only 64KiB in my param.h. I have to agree with HPS. There are many old bridge-chips still in use and problems with a large MAXBSIZE might occur. It's certainly not uncommon to see capacity limitations - I have a docking station which can't see more than 3TB. -- Gary Jennejohn
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