[Lustre-discuss] Clarification on DDN performance best practices

[Mag Gam]

What kernel does DDN use for its products? Or is that a closed secret?


On Mon, Apr 13, 2009 at 10:17 AM, Kit Westneat <kwestneat at ddn.com> wrote:
>
>> As to this, the tier are organized as something similar to 8+2 RAID6.
>> For 8-way data, which is the unit? Sectors? Blocks? In other words, what
>> is the stripe data size in KiB with a sector size of 512 vs. a sector
>> size of 4KiB?
>>
> The S2A directRAID6 is actually based on RAID3, so we use byte striping
> instead of block striping. The 4k alignment comes from the physical disk
> sector size of 512-bytes (512 * 8 = 4k). The S2A has a cache segment
> size, which while independent of the LUN sector size, is sort of similar
> in some ways to a block size on a RAID5, though it will never do a
> read-modify-write. The cache size can be set between 128k - 2M, and for
> Lustre, we usually set it to 1 or 2M, since Lustre currently operates
> with 1M messages.
>
> This picture sort of describes from a high level what happens on the
> data path (the text is very marketing heavy unfortunately):
> http://ddn.com/index.php?id=48
>
> If you are going to be at LUG, DDN will have a fair number folks
> including myself there, feel free to come say hi. We'll also be talking
> at 1 on Friday.
>
> HTH,
> Kit
>
> --
> ---
> Kit Westneat
> kwestneat at datadirectnet.com
> 812-484-8485
>
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