Clemens Eisserer
2014-07-13 12:42:13 UTC
Hi,
A friend of mine uses an old P4 based laptop for email and web browsing.
Thanks to zram, I was able to reduce swapping to disk - however with
just 512mb ram there is not a lot space for the page cache so the disk
is frequently active re-reading data which would stay in pagecache
otherwise.
Would it make sence to use an old usb pen drive - or even two of them
- as read-cache in writearound mode?
Those pen drives usually suffer from very low random write throughput,
but usually offer arround ~1000IOps for 4k random reads and ~20mb/s
sequentially.
Even if they would die within a few months, I have dozens of them and
data integrity shouldn't be compromized with writearound mode.
Does bcache wait for the caching device (stall the read-in-progres)
when filling the cache by writing to the caching device?
In case the caching device isn't respondig in time (writes to cheap
pen block the device for ~500ms), is bcache able to read from the hdd
instead?
Thank you in advance, Clemens
A friend of mine uses an old P4 based laptop for email and web browsing.
Thanks to zram, I was able to reduce swapping to disk - however with
just 512mb ram there is not a lot space for the page cache so the disk
is frequently active re-reading data which would stay in pagecache
otherwise.
Would it make sence to use an old usb pen drive - or even two of them
- as read-cache in writearound mode?
Those pen drives usually suffer from very low random write throughput,
but usually offer arround ~1000IOps for 4k random reads and ~20mb/s
sequentially.
Even if they would die within a few months, I have dozens of them and
data integrity shouldn't be compromized with writearound mode.
Does bcache wait for the caching device (stall the read-in-progres)
when filling the cache by writing to the caching device?
In case the caching device isn't respondig in time (writes to cheap
pen block the device for ~500ms), is bcache able to read from the hdd
instead?
Thank you in advance, Clemens