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MySQL 5.7 中 InnoDB 的 innodb_page_size 在 SSD 硬碟上對效能的巨大影響

Percona 的「Small innodb_page_size as a performance boost for SSD」這篇文章裡提到了 MySQL 5.7 的 innodb_page_size 在 SSD 上對效能的差異,主要是這張圖的解釋:

先講一下標示的部份,有三個產品線 (都是 Samsung 的 SSD),中間的 sam850 是消費級的 SSD 硬碟 (所以不是本次重點),而 sam863 是企業級 SATA SSD,pm1725 則是企業級 PCI-e SSD。下方的 BP 指的是 Buffer Pool 大小,單位是 GB。左邊是速度,數字愈大愈好。

InnoDB 預設 16KB 的 page size,配合 SSD 大多都是 4KB 的 block size 後,效能的提昇非常巨大 (70% 的提昇),雖然既有的 InnoDB 要換過去會花不少功夫,但作者還是很建議評估:

I think a 70% performance gain is too significant to ignore, even if manipulating innodb_page_size requires extra work. I think it is worthwhile to evaluate if using different innodb_page_size settings help a fast SSD under your workload.

不過 comment 有不少額外重要的資訊。

有提到 Galera Cluster 目前有 bug,無法使用 4KB page size,可以在「Restarting a cluster with innodb_page_size=4096 segfaults」這邊看到 bug report。

另外有提到,使用 InnoDB Compression 的前提下,4KB 也許不是個好主意,用 8KB 也許是個方向:

You’re right – if you’re using Innodb Compression 4K base page is unlikely to be the good choice. Though we do not see Innodb compression (any of them) being used too frequently.

If using compression 8K base page size with 4K compressed page size might be good idea if 2x compression is routinely reached

不過我覺得應該還是有幫助才對 (可能提昇不高,但想了一下應該不會有負面的影響),之後有機會再測試看看吧 :o

單顆最大容量的 SSD:15TB

看到 Samsung 弄出單顆 15TB 的 SSD 來嚇大家:「Samsung ships the world's highest capacity SSD, with 15TB of storage」,Samsung 的官方新聞稿在這:「Samsung Introduces World’s Largest Capacity (15.36TB) SSD for Enterprise Storage Systems」。

2.5 吋的 SAS 界面,表示在不考慮預算的情況下,差不多比現在最大的傳統硬碟大了一倍:

The 2.5-in SSD is based on a 12Gbps Serial Attached SCSI (SAS) interface for use in enterprise storage systems.

所以用 2U 伺服器塞 24 顆的情況如何?感覺好讚啊 XDDD

Etsy 用 SSD 的故事

EtsyLaurie Denness 對於 Etsy 使用各種品牌 SSD 的情況給出了他的經歷:「SSDs: A gift and a curse」。

重點在於開頭說的:

SSD firmware is buggy

可以看到當 SSD 配上 RAID controller 的時候,常常會需要找問題... (而且很難找)

Intel 的評價很不錯:

Okay, bad start, we’ve actually had no issues with Intel. This seems to be common across other companies we’ve spoken to.

OCZ 倒了,被 Toshiba 收購,而且 S.M.A.R.T. 資訊很差,很難預測什麼時候會掛掉 (有助於提前替換):

However, they had poor SMART info (none) so predicting failures was hard.

HP 是個大黑盒:

Unfortunately, HP have proprietary RAID controllers, and they don’t support SMART. Or rather, they refuse to talk to non-HP drives using off the shelf technology, they have their own methods.

Samsung 的評價不錯,C/P 值很高,而且有 S.M.A.R.T.:

Samsung saved the day and picked up from OCZ with a ludicrously cheap 960GB offering, the 840 EVO. A consumer drive, so very limited warranty, but for the price (~$400-500) you got great IOPS and they were reliable. They had better SMART info, and seemed to play nicely with our hardware.

不過 BB6Q 版的韌體搞爆了效能,雖然最後修好了:「Samsung Releases Firmware Update to Fix the SSD 840 EVO Read Performance Bug」。

LiteOn 則是掛在 GC 上 (RAID 裡同時掛掉兩顆以上):

The SSDs were having extended garbage collection periods, exacerbated by a smaller amount of SSDs with higher IO, in RAID6. This caused the controller to kick the drive out of the array… and unfortunately due to the write levelling across the drives, at least two of them were garbage collecting at the same time, destroying the array integrity.

不過後來 Dell 與 LiteOn 分別就 RAID controller 與 SSD 本身都跳下去修正,最後還是解決了:

Dell and LiteOn together identified and fixed weaknesses in their RAID controller, the backplane and the SSD firmware.

算是經驗分享,在 SSD 硬碟成熟的過程中間必經的道路 XD

SSD 硬碟的「寫到掛」測試

Slashdot 上的「Endurance Experiment Kills Six SSDs Over 18 Months, 2.4 Petabytes」看到的,針對萬元以下的 SSD 硬碟大量寫入測試 (算是家用級別?),在經過 18 個月後總算都掛光了...

報導出自「The SSD Endurance Experiment: They're all dead」:

最快死透的是 Intel 的,不過也到了 800TB 的寫入量才掛,如果以每天寫 1TB 的量來算也超過兩年了,看了一下我們家比較忙的 database server 也沒這個量啊,這幾年改善好多...

歡樂的 Samsung Security Hole...

話說 Zite 給的文章愈來愈歡樂了,大概是安全性的文章點多了就自動丟這類的出來。

像是這篇「[ROOT][SECURITY] Root exploit on Exynos」講安全漏洞的,作者猜測這些手機都有問題:

  • Samsung Galaxy S2
  • Samsung Galaxy Note 2
  • MEIZU MX
  • 使用 Samsung source code 的 Exynos processor

後門是 /dev/exynos-mem,這功能與 /dev/mem 一樣,只是... 所有人都可以讀寫 XD (於是任何程式都可以讀寫整台機器裡任何一個記憶體區塊內的資料)

然後文章後面提供一包 PoC source,可以生出 root shell... XDDD

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