[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Xen-users] Cheap IOMMU hardware and ECC support importance

  • To: xen-users@xxxxxxxxxxxxx
  • From: Kuba <kuba.0000@xxxxx>
  • Date: Sat, 28 Jun 2014 11:32:27 +0200
  • Delivery-date: Sat, 28 Jun 2014 09:33:03 +0000
  • List-id: Xen user discussion <xen-users.lists.xen.org>

W dniu 2014-06-28 09:45, lee pisze:

and your workload includes a lot of synchronous writes. But
for that workload you would probably be better off getting an
SSD and using ZFS with ZIL in terms of total cost, performance
and reliability.

SSDs still loose badly when you compare price with capacity.  For what I
payed for the RAID controller, I could now buy two 120GB SSDs (couldn't
back then).  That means two disks more, requiring two more SATA ports
(11 in total), and an increased overall chance of disk failures because
the more disks you have, the more can fail.

I don't know about ZFS, though, never used that.  How much CPU overhead
is involved with that?  I don't need any more CPU overhead like comes
with software raid.

ZFS offers you two things RAID controller AFAIK cannot do for you: end-to-end data checksumming and SSD caching. If anything happens with your data on its round trip from the CPU to the disk and back, ZFS will detect that and, provided you have some redundancy, will correct it. That feature alone, IMHO, makes reading about ZFS worthwhile. As Gordan states, ZFS can also cache your data using a small SSD. Oversimplifying, the size of the SSD might be around the size of your data set.

Moreover, it blends in with xen quite nicely, e.g. using ZFS ZVOLs as block devices for domUs makes cloning and snapshotting easy (and that's just for starters).


Xen-users mailing list



Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.