I think he meant that they might not have one.<p>It&#x27;s been a while since I looked at using ZFS for anything meaningful, but at the time (~6 years ago), while losing L2ARC was no big deal, losing dedicated ZIL was catastrophic. I think that&#x27;s still true today.<p>So you need at least two ZIL devices in a mirror. On top of that, you really need something faster and lower latency for your ZIL vs. the ARC or main pool; people were trying to use SSDs but most commonly-available drives at the time would either degrade or fail in a hurry under load. So the options were RAM-based, e.g. STEC ZeusRAM on the high end, or some sort of PCI-X&#x2F;PCIe RAM device. The former was not easy or cheap to acquire for testing stuff, and the latter made failover configs impossible.<p>I think that ZIL is also not soaking up all writes, just most writes meeting a certain criteria. Some just stream through to the pool. So I was always thinking of it as a protection device that also converted random writes to sequential. Some people don&#x27;t think they need that.<p>I remember the fragmentation issue being a problem at the time, but also thinking it was probably going to get solved soon because there was so much interest and a whole company behind it. Then Oracle happened. My guess is that if it were still Sun and all the key people were still there, this would be a solved problem right now. As it is, Oracle probably wants you to buy all the extra storage anyway, and would love to offer professional services to get you out of the fragmentation bind you&#x27;re in.