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SubjectRe: Disk schedulers
Lukas Hejtmanek wrote:
> whom should I blame about disk schedulers?
> I have the following setup:
> 1Gb network
> disk write speed about 20MB/s
> If I'm scping file (about 500MB) from the network (which is faster than the
> local disk), any process is totally unable to read anything from the local disk
> till the scp finishes. It is not caused by low free memory, while scping
> I have 500MB of free memory (not cached or buffered).
> I tried cfq and anticipatory scheduler, none is different.
> ----
You didn't say anything about #processors or speed, nor
did you say anything about your hard disk's raw-io ability.
You also didn't mention what kernel version or whether or not
you were using the new UID-group cpu scheduler in 2.6.24 (which likes
to default to 'on'; not a great choice for single-user, desktop-type
machines, if I understand its grouping policy).

Are you sure neither end of the copy is cpu-bound on ssh/scp
encrypt/decrypt calculations? It might not just be inability
to read from disk, but low cpu availability. Scp can be alot
more CPU intensive than you would expect... Just something to


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