Changes between Version 18 and Version 19 of FAQ

Timestamp:

Oct 3, 2009, 11:58:56 AM (15 years ago)

Author:

Gabriele Pohl

Comment:

Added note on increasing block size in the future

FAQ

@@ -319 +319 @@
 === {{{Unreadable, uncorrectable, pending}}} sectors or {{{Medium error}}} on disk. What's going on? ===
 
-SCSI and ATA disk drives store data in blocks (sectors) of 512 bytes. Each 512 bytes of user data is stored on the media plus 40 or more bytes of ECC data included in it. These - so called ''ECC Bytes'' - are used internally by the disk firmware for error checking/detection and correction.
+SCSI and ATA disk drives store data in blocks (sectors) of 512^[#blocksize (1)]^ bytes. Each 512 bytes of user data is stored on the media plus 40 or more bytes of ECC data included in it. These - so called ''ECC Bytes'' - are used internally by the disk firmware for error checking/detection and correction.
 
 Sometimes the data in a sector gets corrupted.  This can happen because a speck of dust scratched the disk, or because the disk was powered down while writing data to that sector, or for other reasons. Usually the ECC bytes can be used to correct the corrupted data. However if the ECC bytes are inconsistent or can't be used to correct the bad data, then the 512 bytes of data are lost.  Such a sector is called unreadable or uncorrectable.
@@ -328 +328 @@
 
 Normally when an uncorrectable sector is found, the disk puts this onto a 'pending sector list' to indicate that it should be replaced with a spare good sector.  However this replacement won't take place until either the disk can read the data on the bad sector, or is instructed to write new data to that bad sector.
-
+{{{
+#!html
+<a name="blocksize">(1)</a> In the future the block size for disks (especially in the terabyte range) will increase from 512 bytes to 4096 bytes.
+}}}
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