[zfs-discuss] Pure SSD Pool

Henry Lau
Tue, 12 Jul 2011 17:10:51 -0000

It is hard to say, 90% or 80%. SSD has already?reserved?overprovisioning places
for garbage collection and wear leveling. The OS level only knows?file LBA, not
the physical LBA mapping to flash pages/block.?Uberblock updates and COW from
ZFS will use a new page/block each time. A TRIM command from ZFS level should be
a better solution but?RAID is still a problem for TRIM at the OS level.

Henry



----- Original Message ----
From: Jim Klimov <jimklimov at cos.ru>
Cc: ZFS Discussions <zfs-discuss at opensolaris.org>
Sent: Tue, July 12, 2011 4:18:28 AM
Subject: Re: [zfs-discuss] Pure SSD Pool

2011-07-12 9:06, Brandon High ?????:
> On Mon, Jul 11, 2011 at 7:03 AM, Eric Sproul<esproul at omniti.com>?
wrote:
>> Interesting-- what is the suspected impact of not having TRIM support?
> There shouldn''t be much, since zfs isn''t changing data in
place. Any
> drive with reasonable garbage collection (which is pretty much
> everything these days) should be fine until the volume gets very full.

I wonder if in this case it would be beneficial to slice i.e. 90%
of an SSD for use in ZFS pool(s) and leave the rest of the
disk unassigned to any partition or slice? This would reserve
some sectors as never-written-to-by-OS. Would this ease the
life for SSD devices without TRIM between them ans the OS?

Curious,
//Jim

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