HD readahead

[Giorgos Keramidas]

On 2006-04-04 00:50, Michael Iatrou <iatrou at serverhive.com> wrote:
> root at wintermute:~# hdparm /dev/hda
>
> /dev/hda:
>  multcount    = 16 (on)
>  IO_support   =  3 (32-bit w/sync)
>  unmaskirq    =  1 (on)
>  using_dma    =  1 (on)
>  keepsettings =  0 (off)
>  readonly     =  0 (off)
>  readahead    = 256 (on)
>  geometry     = 24321/255/63, sectors = 390721968, start = 0
>
> root at wintermute:~# hdparm -i /dev/hda
>
> /dev/hda:
>
>  Model=ST3200827A, FwRev=3.AAD, SerialNo=3ND2FR06
>  Config={ HardSect NotMFM HdSw>15uSec Fixed DTR>10Mbs RotSpdTol>.5% }
>  RawCHS=16383/16/63, TrkSize=0, SectSize=0, ECCbytes=4
>  BuffType=unknown, BuffSize=8192kB, MaxMultSect=16, MultSect=16
>  CurCHS=65535/1/63, CurSects=4128705, LBA=yes, LBAsects=268435455
>  IORDY=on/off, tPIO={min:240,w/IORDY:120}, tDMA={min:120,rec:120}
>  PIO modes:  pio0 pio1 pio2 pio3 pio4
>  DMA modes:  mdma0 mdma1 mdma2
>  UDMA modes: udma0 udma1 udma2 udma3 udma4 *udma5
>  AdvancedPM=no WriteCache=enabled
>  Drive conforms to: device does not report version:
>
>  * signifies the current active mode
>
> To μηχανάκι είναι ένα single-user workstation. Ο δίσκος έχει 8MB cache, αλλά
> όπως φαίνεται, από το readahead, κάνει prefetch μόνο 128Kbytes.

Μπορεί ένα μέρος από τα 8 MB cache να χρησιμοποιείται για το write
caching (WriteCache=enabled) κι όχι για read-ahead.