Date: Wed, 18 Jun 2008 22:26:21 +0200 From: "Julian Stacey" <jhs@berklix.org> To: freebsd-usb@freebsd.org Subject: Re: best block size for file systems on USB media ? Message-ID: <200806182026.m5IKQLw5016490@fire.js.berklix.net> In-Reply-To: Your message "Wed, 18 Jun 2008 01:48:46 %2B0200." <200806180148.46908.hselasky@c2i.net>
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Hans Petter Selasky wrote: > On Tuesday 17 June 2008, Julian Stacey wrote: > > Hi usb@freebsd.org > > Do USB flash memory sticks have cache ram ? What are best file > > system block sizes to write USB media (to maximise access speed) ? > > Any URLS to RTFM welcome ;-) > > > > I'm using mine to back up my personal tree of private data, (mail > > & tech notes & sources etc, lots of smallish files), I'm using > > /usr/ports/net/rdist6 to backup. > > > > My biggest stick, a 2G Sandisk Cruzer micro (vendor 0x0781 product > > 0x5151) is awfully slow (much slower per Meg than other manufacturers > > smaller sticks) (& other 2G Sandisk sticks bought in same purchase > > from same vendor are also awfully slow on Win-XP, so maybe these > > have less or no cache ram (if such things have cache at all ?) or > > maybe they were a fraudulent batch without cache when they should > > have had cache or ... ? ) Maybe some other sticks work on different > > block size ? Maybe for many of my small files, the stick needs to > > read a big block, before modifying a small chunk & writing back to > > block ? > > > > Block sizes was a question I'd meant to ask earlier, just for normal > > sticks with a normal FreeBSD FS on there, now it's become even more > > of an interest, using a BSD FS within an encrypted gbde partition > > ref. Read > > http://www.freebsd.org/doc/en/books/handbook/disks-encrypting.html which > > is slower still from encyption overhead (noticeable doing a reload > > into new empty FS). > > > > Some FS issues might be better discussed later on fs@freebsd.org, > > but first, what's known about USB hardware block sizes please ? > > Hi, > > The blocksize for USB Flash is typically 512 bytes due to wMaxPacketSize being > 512 bytes at High Speed USB. > > The SCSI command set allows you to read up to 32MByte in one go, but FreeBSD > typically does not read/write more than 64K. OK, thanks so that's FreeBSD side covered, newfs & FFS etc use several K & I'm recently using gbde with 2K so no problem with that from the FreeBSD side of the interface. But what if the internal stick hardware works on say 10K chunks ? is there anyone on this list who knows how USB sticks work internaly ? ( I remember at least one chap some time back, on some freebsd list, being quite authoritative on max read write patterns before failure, maybe he knows about blocking & if there's cache too ? ) Julian -- Julian Stacey: BSDUnixLinux C Prog Admin SysEng Consult Munich www.berklix.com Mail just Ascii plain text. HTML & Base64 text are spam.
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