[ZFS] Using SSD with partitions

[Daniel Kalchev]

On Oct 16, 2011, at 21:02 , Luchesar V. ILIEV wrote:

> On 16/10/2011 19:17, Daniel Kalchev wrote:
>> Therefore, with ZFS v28, adding ZIL does not introduce any more risk
>> to your data.
> 
> I might be wrong in my interpretation, but from what I remember, when
> the power goes down, an unprotected SSD is likely to lose _more_ data
> than simply its write buffers -- that's quite unlike a hard-drive. So
> much, in fact, that the whole ZIL might become corrupted (and that's
> potentially way more data than any device cache).

The real risk with low-grade "unprotected" SSDs is that the SSD may well become damaged, sometimes beyond repair.

It is the same risk with SSDs or with magnetic drives. If the drive lies to the OS that it has safely written data -- then data will be lost. Thing is, we know what a cheap HDD is. Most SSDs however lie, because otherwise they will offer very poor write performance.

ZIL is not about RAM. ZIL is for low latency synchronous writing. It does not matter how much RAM do you have -- it will not help if you have heavy synchronous writing (of small records).  

Anyway, as it was mentioned -- with moderate activity on the pool, it is not problem to use the same SSD for boot/ZIL/L2ARC.


Daniel