Date: Fri, 31 Jan 2003 11:30:18 -0500 From: Steve Byan <stephen_byan@maxtor.com> To: freebsd-fs@FreeBSD.ORG, tech-kern@netbsd.org Subject: DEV_B_SIZE Message-ID: <4912E0FE-3539-11D7-B26B-00306548867E@maxtor.com>
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There's a notion afoot in IDEMA to enlarge the underlying physical block size of disks to 4096 bytes while keeping a 512-byte logical block size for the interface. Unaligned accesses would involve either a read-modify-write or some proprietary mechanism that provides persistence without the latency cost of a read-modify-write. Performance issues aside, it occurs to me that hiding the underlying physical block size may break many careful-write and transaction-logging mechanisms, which may depend on no more than one block being corrupted during a failure. In IDEMA's proposal, a power failure during a write of a single 512-byte logical block could result in the corruption of the full 4K block, i.e. reads of any of the 512-byte logical blocks in that 4K physical block would return an uncorrectable ECC error. I'd appreciate hearing examples where hiding the underlying physical block size would break a file system, database, transaction processing monitor, or whatever. Please let me know if I may forward your reply to the committee. Thanks. Regards, -Steve -------- Steve Byan <stephen_byan@maxtor.com> Design Engineer Maxtor Corp. MS 1-3/E23 333 South Street Shrewsbury, MA 01545 (508) 770-3414 To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-fs" in the body of the message
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