Spin up all raid drives at the same time

Question

Here is the configuration:

4 HDDs in a RAID-5 array (mdadm)
hdparm spin_down_time set for all disks
Debian jessie 8.11

When the drives are in standby mode and the RAID array is requested, they wake up "sequentially", one after another.
It makes the access delayed for many seconds.

Is there a way to make all the drives spin up at the same time ?

@michael-hampton When the server is left idle for a while, the drives go into standby mode (spin down). This is the hdparm expected behavior. — Tigger, Jun 30 '21 at 17:50
That is _not_ normal behavior. The drives should always be spinning. — Michael Hampton, Jun 30 '21 at 17:59

score 2 · Answer 1 · answered Jun 30 '21 at 21:43

2

The drive does a staggered spinup likely because you access sequential data chunks. Suppose having a stripe size of 64K (single disk chunk size of 16K): a single 64K read will sequentially wake all disks.

To avoid spinning down the disks you can use hdparm -B 128 to selectively disable spin down only. For maximum performance you can issue hdparm -B 255, which completely disables any power-saving measures.

answered Jun 30 '21 at 21:43

shodanshok

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Thank you for your explanation, it makes sense. mdadm tries to read the first chunk on the first drive, waits for it to be available, then tries to read the next one. Then I don't think there is any mdadm/hdparm option that could help (without disabling spinning down). Do you ? – Tigger Jun 30 '21 at 23:12
on an RAID and what you called "server" disk never spinning down – djdomi Jul 01 '21 at 04:49

Spin up all raid drives at the same time

1 Answers1