On Wed, 26 Jun 2013 15:12:53 +0100, Lew Wolfgang wrote:

Hi Folks,

Back in the '80s we configured swap space to be 1.5 x RAM as a rule of thumb. But I'm configuring 6 boxes now that contain 64-GB of RAM and I'm wondering if swap should be anything close to 96-GB. The boxes have only 128-GB of SSD for the operating system, so I'd like to minimize swap as much as possible.

As background, these devices will be used as dedicated data acquisition devices. They will pump data from four Gig-E Ethernet ports and store it all in a 24-disk RAID-6 array. Preliminary measurements show we should be able to maintain continuous throughput until the RAID is full.

So, any opinions on swap size in relation to RAM?

Thanks, Lew

With that much RAM, you probably don't even need swap...surely -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse+owner@opensuse.org

Typically we just give 2GB and let it be; I've heard extensive discussions in other Novell listservs that vary anywhere between that number all the way down to sometimes not allocating any swap at all. But we go the 2GB route just to be safe, irregardless of how much memory a box has. A big exception would be SuSE servers that host Oracle databases however; those still have the huge swap requirements. Chris

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Lew Wolfgang 06/26/13 9:14 AM >>> Hi Folks,

Back in the '80s we configured swap space to be 1.5 x RAM as a rule of thumb. But I'm configuring 6 boxes now that contain 64-GB of RAM and I'm wondering if swap should be anything close to 96-GB. The boxes have only 128-GB of SSD for the operating system, so I'd like to minimize swap as much as possible. As background, these devices will be used as dedicated data acquisition devices. They will pump data from four Gig-E Ethernet ports and store it all in a 24-disk RAID-6 array. Preliminary measurements show we should be able to maintain continuous throughput until the RAID is full. So, any opinions on swap size in relation to RAM? Thanks, Lew -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse+owner@opensuse.org -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse+owner@opensuse.org

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On Wednesday, 2013-06-26 at 07:12 -0700, Lew Wolfgang wrote:

So, any opinions on swap size in relation to RAM?

As much as you need ;-) How much do I need? Good question. Anything from none to 10 times the ram. If you are going to hibernate the machine you need a bit more than ram. Swap can also be used to push there unneeded blocks, so that you end with more free ram. Use, say, 4 GiB. To say something ;-) You can set some, use the machine for some time, and watch how much swap, if any, is used. Then redo the partitioning if necesary. - -- Cheers, Carlos E. R. (from 12.3 x86_64 "Dartmouth" at Telcontar) -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.19 (GNU/Linux) iEYEARECAAYFAlHLBH0ACgkQtTMYHG2NR9Xk6ACeLQGJwoKqYFEoYtOvpKMaU58/ TEgAn1V7WRTTndIHgkr9AtYaIn0JApaI =tZlz -----END PGP SIGNATURE----- -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse+owner@opensuse.org

This system runs 6 web browsers loaded with more tabs than can be identified by the miniscule visible text they contain, email, 2 IRC apps, and several other apps 24/7 with 4GB RAM and 0 enabled dedicated HD swap space. Occasionally when working with large A/V files I see disk cache shrink to less than 15% or so, but usually more RAM is used by cache than any single application. Uptime is currently 19 days and cache is 35% of total RAM. If swap is ever actually needed, the kernel will swap to /. With 64GB RAM, I find it difficult to imagine need for non-zero arbitrary allocation of dedicated swap space for a system that won't be hibernated. -- "The wise are known for their understanding, and pleasant words are persuasive." Proverbs 16:21 (New Living Translation) Team OS/2 ** Reg. Linux User #211409 ** a11y rocks! Felix Miata *** http://fm.no-ip.com/ -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse+owner@opensuse.org

El 26/06/13 10:12, Lew Wolfgang escribió:

Hi Folks,

Back in the '80s we configured swap space to be 1.5 x RAM as a rule of thumb. But I'm configuring 6 boxes now that contain 64-GB of RAM and I'm wondering if swap should be anything close to 96-GB. The boxes have only 128-GB of SSD for the operating system, so I'd like to minimize swap as much as possible.

Unless the 64 GB RAM boxes are really, really busy I do not think you need swap. -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse+owner@opensuse.org

-----Original Message----- From: Lew Wolfgang Reply-to: wolfgang@sweet-haven.com To: OS-en Subject: [opensuse] How Much Swap? Date: Wed, 26 Jun 2013 07:12:53 -0700 Hi Folks, Back in the '80s we configured swap space to be 1.5 x RAM as a rule of thumb. But I'm configuring 6 boxes now that contain 64-GB of RAM and I'm wondering if swap should be anything close to 96-GB. The boxes have only 128-GB of SSD for the operating system, so I'd like to minimize swap as much as possible. As background, these devices will be used as dedicated data acquisition devices. They will pump data from four Gig-E Ethernet ports and store it all in a 24-disk RAID-6 array. Preliminary measurements show we should be able to maintain continuous throughput until the RAID is full. So, any opinions on swap size in relation to RAM? -----Original Message----- Indeed Lew, that amount of swap would be rediculous. However, still swap area should be considered as a "safety-lane" So keep one of a couple a gigs and turn the "swappiness" of the system low (5). Often it is "60", see: /proc/sys/vm/swappiness -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse+owner@opensuse.org